Low Density And High Strength Fiber Glass For Reinforcement Applications

ABSTRACT

The present invention relates to fiber glass strands, yarns, fabrics, composites, prepregs, laminates, fiber-metal laminates, and other products incorporating glass fibers formed from glass compositions. The glass fibers, in some embodiments, are incorporated into composites that can be used in reinforcement applications. Glass fibers formed from some embodiments of the glass compositions can have certain desirable properties that can include, for example, desirable electrical properties (e.g. low D k ) or desirable mechanical properties (e.g., specific strength).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 61/382,738, filed on Sep. 14, 2010, the entire disclosure ofwhich is hereby incorporated by reference. This application claimspriority to and is a continuation-in-part of U.S. patent applicationSer. No. 13/229,012, filed on Sep. 9, 2011, which is acontinuation-in-part of U.S. patent application Ser. No. 12/940,764,filed on Nov. 5, 2010, which is a continuation of U.S. patentapplication Ser. No. 11/610,761, filed on Dec. 14, 2006, now U.S. Pat.No. 7,829,490, which issued Nov. 9, 2010, the contents of which are eachhereby incorporated by reference in their entireties.

FIELD OF INVENTION

The present invention relates to low density and high strength glassfibers and yarns, fabrics, and composites comprising low density andhigh strength glass fibers adapted for use in reinforcementapplications.

BACKGROUND

Glass fibers have been used to reinforce various polymeric resins formany years. Some commonly used glass compositions for use inreinforcement applications include the “E-glass” and “D-glass” familiesof compositions. Another commonly used glass composition is commerciallyavailable from AGY (Aiken, S.C.) under the trade name “S-2 Glass.”

Glass fibers have been arranged to form fabrics for many years. Inconventional glass fiber weaving operations, a glass fabric is woven byinterweaving weft yarns (also referred to as “fill yarns”) into aplurality of warp yarns. Generally, this is accomplished by positioningthe warp yarns in a generally parallel, planar array on a loom, andthereafter weaving the weft yarns into the warp yarns by passing theweft yarns over and under the warp yarns in a predetermined repetitivepattern. The pattern used will depend upon the desired fabric style.

Warp yarns are typically formed by attenuating a plurality of moltenglass streams from a bushing or spinner. Thereafter, a coating (orprimary sizing composition) is applied to the individual glass fibersand the fibers are gathered together to form a strand. The strands aresubsequently processed into yarns by transferring the strands to abobbin via a twist frame. During this transfer, the strands can be givena twist to aid in holding the bundle of fibers together. These twistedstrands are then wound about the bobbin and the bobbins are used in theweaving processes.

Positioning of the warp yarns on the loom is typically done by way of aloom beam. A loom beam comprises a specified number of warp yarns (alsoreferred to as “ends”) wound in an essentially parallel arrangement(also referred to as “warp sheet”) about a cylindrical core. Loom beampreparation typically requires combining multiple yarn packages, eachpackage comprising a fraction of the number of ends required for theloom beam, into a single package or loom beam. For example and althoughnot limiting herein, a 50 inch (127 cm) wide, 7781 style fabric whichutilizes a DE75 yarn input typically require 2868 ends. However,conventional equipment for forming a loom beam does not allow for all ofthese ends to be transferred from bobbins to a single beam in oneoperation. Therefore, multiple beams comprising a fraction of the numberof required ends, typically referred to as “section beams,” are producedand thereafter combined to form the loom beam. In a manner similar to aloom beam, a section beam typically includes a cylindrical corecomprising a plurality of essentially parallel warp yarns woundthereabout. While it will be recognized by one skilled in the art thatthe section beam can comprise any number of warp yarns required to formthe final loom beam, generally the number of ends contained on a sectionbeam is limited by the capacity of the warping creel. For a 7781 stylefabric, four section beams of 717 ends each of DE75 are typicallyprovided and when combined offer the required 2868 ends for the warpsheet, as discussed above.

As previously discussed, a primary sizing composition is applied to theglass fibers, typically immediately after forming. Traditionally, thefilaments forming the continuous glass fiber strands used in weavingfabric are treated with an aqueous starch-oil sizing, which typicallyincludes partially or fully dextrinized starch or amylose, hydrogenatedvegetable oil, a cationic wetting agent, emulsifying agent, and water,as is well known to those skilled in the art. For more informationconcerning such sizing compositions, see K. Loewenstein, TheManufacturing Technology of Continuous Glass Fibres, (3d Ed. 1993) atpages 237-244, which is specifically incorporated by reference herein.While such sizing compositions are generally robust enough to provideprotection to the fibers during fiber forming and loom beammanufacturing processes, they normally are unable to protect the glassfibers, and in particular the warp yarn fibers, from abrasion and wearduring high speed weaving. As a result, it is conventional practice inthe textile weaving industry to pass the warp yarn through a slasher,which applies a slashing size to the warp yarns during the manufactureof the loom beam to provide the additional protection required, in amanner to be discussed later in more detail. More particularly, theslashing operation provides the vehicle to add additional film formingchemistry to the fibers forming the warp yarn sheet. Typically, theslashing size includes either fully or partially hydrolyzed polyvinylalcohol (PVA) materials and is a mixture in the 6-8% solids range with aviscosity of 15 to 20 centipoise (CPS). The slashing size is typicallyapplied by submerging the warp yarn sheet in a vessel containing theslashing size via a series of submersion rollers and then passing itthrough a squeeze roll system, which typically exerts 15 to 20 poundsper square inch of squeezing pressure on the coated yarn in addition tothe dead weight of the squeeze roller (the squeeze pressure can vary dueto yarn diameter), to remove the excess slashing size. The slashing sizecan be applied at an elevated temperature, e.g., in the range of 130 to150° F. (54 to 66° C.) or at room temperature, depending upon therecommendations of the PVA producer. After squeezing the excess sizefrom the yarn sheet, the slashing sized sheet is dried in any convenientmanner known in the art, such as but not limited to passing the sheetover heated rollers and/or through a hot air drying oven. In a slasherincorporating heated rollers, or cans, the surface temperature of thecans is typically in the range of 240 to 280° F. (116 to 138° C.). Theactual temperature profile of the drying cans depends in part on the canarrangement, number of cans, and yarn speed. In a hot air drying oven,the air temperature within the oven typically ranges from 275 to 300° F.(135 to 149° C.). After drying, the warp yarn sheet passes through aseries of split rods to separate the warp sheets and through a hook reedassembly and comb to combine the warp sheets and assure that no ends areadhered to each other. The yarn sheet is then wound onto the loom beam.

Both the primary starch-oil coating and slashing size are not compatiblewith polymeric resin matrix materials used to impregnate woven fabricincorporating the coated yarns. As a result, these coatings must beremoved from the fabric, e.g., by heat cleaning and/or scrubbing, priorto incorporation of a fabric woven from these yarns into the matrixmaterial. For example, a typical one-step heat cleaning process canentail heating the fabric at 600 to 800° F. (316 to 427° C.) for 70-80hours to remove the starch-oil primary sizing composition and slashingsize. In an alternative two-step operation, the fabric is unrolledthrough an oven where it is exposed to a flame that burns off a portionof the sizes, and then heated at 600 to 800° F. (316 to 427° C.) for 50to 60 hours. The first step of this two-step operation is sometimesreferred to as caramelizing and is typically used to heat clean fabricswoven from coarse yarns, i.e., 7628 style fabric.

When a primary sizing composition that is compatible with the resinmatrix material is applied to the individual glass fibers duringforming, it has been found that the application of additional slashingsize to protect the glass fibers is unnecessary. As a result, the needfor additional fiber protection through the application of a slashingsize is eliminated. However, it has been observed that when such warpyarns having a resin compatible coating are simply wound onto a loombeam from multiple section beams, for example by passing the warp yarnthrough a slasher without the addition of slashing size, heating, anddrying (sometimes referred to as “dry slashing”) to form a loom beam,the number of loom beam defects, such as end breaks due to rolled andtwisted ends, is excessive. Rolled ends, which is a condition whereinadjacent glass strands roll on top of each other and are twistedtogether, are particularly troublesome as they can lead to end breaksduring weaving, which in turn are associated with fabric quality issuessuch as ends out, fuzzy ends, chaffed ends, and undesirable yarnsplices.

Nevertheless, the capability to make loom beams with warp yarns having aresin compatible coating on a slasher without using slashing size isimportant since the main method of forming loom beams in the textileweaving industry is by use of a slasher, and most weaving operationsalready have this type of equipment.

SUMMARY

Various embodiments of the present invention relate generally to lowdensity and high strength glass fibers, and to fiber glass strands,yarns, fabrics, and composites comprising low density and high strengthglass fibers adapted for use in reinforcement applications.

Some embodiments of the present invention relate to fiber glass strands.A number of fiberizable glass compositions are disclosed herein as partof the present invention, and it should be understand that variousembodiments of the present invention can comprise glass fibers, fiberglass strands, yarns, and other products incorporating glass fibersformed from such compositions.

In one aspect, a fiber glass strand of the present invention comprises aplurality of glass fibers comprising a glass composition that comprisesthe following components:

SiO2 60-68 weight percent; B2O3 7-12 weight percent; Al2O3 9-15 weightpercent; MgO 8-15 weight percent; CaO 0-4 weight percent; Li2O 0-2weight percent; Na2O 0-1 weight percent; K2O 0-1 weight percent; Fe2O30-1 weight percent; F2 0-1 weight percent; TiO2 0-2 weight percent; andother constituents 0-5 weight percent total;wherein the (Li2O+Na2O+K2O) content is less than 2 weight percent andwherein the MgO content is at least twice the content of CaO on a weightpercent basis.

In another aspect, a fiber glass strand of the present inventioncomprises a plurality of glass fibers comprising a glass compositionthat comprises the following components:

SiO2 53.5-77 weight percent; B2O3 4.5-14.5 weight percent; Al2O34.5-18.5 weight percent; MgO 4-12.5 weight percent; CaO 0-10.5 weightpercent; Li2O 0-4 weight percent; Na2O 0-2 weight percent; K2O 0-1weight percent; Fe2O3 0-1 weight percent; F2 0-2 weight percent; TiO20-2 weight percent; and other constituents 0-5 weight percent total.

In some embodiments, the plurality of glass fibers can have a diameterbetween about 5 microns and about 13 microns. In some embodiments, thefiber glass strand is at least partially coated with a sizingcomposition.

Some embodiments of the present invention relate to yarns formed from atleast one fiber glass strand formed from a glass composition describedherein. Some embodiments of the present invention relate to fabricsincorporating at least one fiber glass strand formed from a glasscomposition described herein. In some embodiments, a fill yarn used inthe fabric can comprise the at least one fiber glass strand. A warpyarn, in some embodiments, can comprise the at least one fiber glassstrand. In some embodiments, fiber glass strands can be used in bothfill yarns and warp yarns used to form fabrics according to the presentinvention. In some embodiments, fabrics of the present invention cancomprise a plain weave fabric, a twill fabric, a crowfoot fabric, asatin weave fabric, a stitch bonded fabric, or a 3D woven fabric.

Some embodiments of the present invention relate to compositescomprising a polymeric resin and glass fibers formed from one of thevarious glass compositions described herein. The glass fibers can befrom a fiber glass strand according to some embodiments of the presentinvention. In some embodiments, the glass fibers can be incorporatedinto a fabric, such as a woven fabric. For example, the glass fibers canbe in a fill yarn and/or a warp yarn that are woven to form a fabric. Inembodiments where the composite comprises a fabric, the fabric cancomprise a plain weave fabric, a twill fabric, a crowfoot fabric, asatin weave fabric, a stitch bonded fabric, or a 3D woven fabric. Theglass fibers can be incorporated into the composite in other forms aswell as discussed in more detail below.

With regard to polymeric resins, composites of the present invention cancomprise one or more of a variety of polymeric resins. In someembodiments, the polymeric resin comprises at least one of polyethylene,polypropylene, polyamide, polyimide, polybutylene terephthalate,polycarbonate, thermoplastic polyurethane, phenolic, polyester, vinylester, polydicyclopentadiene, polyphenylene sulfide, polyether etherketone, cyanate esters, bis-maleimides, and thermoset polyurethaneresins. The polymeric resin can comprise an epoxy resin in someembodiments.

Composites of the present invention can be in a variety of forms and canbe used in a variety of applications. For example, and withoutlimitation, the composites can include aerospace composites, aviationcomposites, radomes, laminates, fiber-metal laminates, and others. As anexample, a fiber-metal laminate can comprise various layers of glassreinforced composites and metal sheets. In one embodiment, a fiber-metallaminate can comprise a prepreg comprising a polymeric resin and afabric comprising a plurality of glass fibers formed from one of thevarious glass compositions described herein, a first metal sheetadhesively secured to one surface of the pregreg, and a second metalsheet adhesively secured to a second surface of the prereg, such thatthe prepreg is positioned between the two metal sheets. In anotherembodiment, a second prepreg and be positioned between the second metalsheet and a third metal sheet. In one embodiment, the metal sheets cancomprise aluminum and the polymeric resin can comprise epoxy.

These and other embodiments are discussed in greater detail in thedetailed description which follows.

DETAILED DESCRIPTION

For the purposes of this specification, unless otherwise indicated, allnumbers expressing quantities of ingredients, reaction conditions, andso forth used in the specification are to be understood as beingmodified in all instances by the term “about.” Accordingly, unlessindicated to the contrary, the numerical parameters set forth in thefollowing specification are approximations that may vary depending uponthe desired properties sought to be obtained by the present invention.At the very least, and not as an attempt to limit the application of thedoctrine of equivalents to the scope of the claims, each numericalparameter should at least be construed in light of the number ofreported significant digits and by applying ordinary roundingtechniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains errorsnecessarily resulting from the standard deviation found in applicabletesting measurements.

It is further noted that, as used in this specification, the singularforms “a,” “an,” and “the” include plural referents unless expressly andunequivocally limited to one referent.

Reinforcing some materials, such as polymeric resins, with glass fiberscan result in composites having improved impact resistance and/or otherdesirable mechanical properties. For some glass fiber reinforcementapplications, it may be desirable to use stronger, lighter weight, andmore cost effective glass fibers. The combination of high strengthand/or high modulus with low density can be especially important forsome aerospace and transportation applications, in which weight is oftenan important design parameter. Compared to glass fibers comprisingE-glass, glass fibers useful in some embodiments of the presentinvention can exhibit high strain-to-failure, high strength, and/or lowfiber density, which combination can result in glass fiber-reinforcedcomposites having a lower areal density for a given fiber volumefraction or a given composite performance. In some embodiments, theglass fibers may be first arranged into a fabric. In some embodiments,glass fibers of the present invention can be provided in other formsincluding, for example and without limitation, as chopped strands (dryor wet), yarns, wovings, prepregs, etc. In short, various embodiments ofthe glass compositions (and any fibers formed therefrom) can be used ina variety of applications.

Fiberizable glass compositions have been developed which provideimproved electrical performance (i.e., low dielectric constant, D_(k),and/or low dissipation factor, D_(f)) relative to standard E-glass,while providing temperature-viscosity relationships that are moreconducive to commercially practical fiber forming than previous lowD_(k) glass proposals. Such glass compositions are described in U.S.Pat. No. 7,829,490 and U.S. patent application Ser. No. 13/229,012,filed Sep. 9, 2011, both of which are incorporated herein by referencein their entireties. Another optional aspect of the glass compositionsdescribed in U.S. Pat. No. 7,829,490 and U.S. patent application Ser.No. 13/229,012 is that at least some of the compositions can be madecommercially with relatively low raw material batch cost.

Some embodiments of the present invention relate to fiber glass strands.Some embodiments of the present invention relate to yarns comprisingfiber glass strands. Some embodiments of yarns of the present inventionare particularly suitable for weaving applications. In addition, someembodiments of the present invention relate to glass fiber fabrics. Someembodiments of glass fiber fabrics of the present invention areparticularly suitable for use in reinforcement applications, especiallyreinforcement applications in which low density and high modulus, highstrength, and/or high strain-to-failure are important. Further, someembodiments of the present invention relate to composites thatincorporate fiber glass strands, glass fiber yarns, and glass fiberfabrics, such as fiber reinforced polymer composites. Some composites ofthe present invention are particularly suitable for use in reinforcementapplications, especially reinforcement applications in which low densityand high modulus, high strength, and/or high strain-to-failure areimportant, such as aerospace, aviation, wind energy, radome, and otherapplications. Some composites of the present invention may be especiallysuitable for use in any application in which high impact resistance andlow density are desirable. Exemplary applications include, among others,aerospace applications, aviation applications, automobile applications,shipping applications, wind energy applications, bridge construction,and radomes. Some embodiments of the present invention relate toaerospace composites. Other embodiments of the present applicationrelate to aviation composites. Still other embodiments of the presentinvention relate to composites suitable for use in wind energyapplications. Some embodiments of the present invention relate toprepregs. Other embodiments of the present invention relate tolaminates. Some embodiments of the present invention relate tofiber-metal laminates (e.g., fiber glass prepregs positioned betweenmetal sheets) that can be used, for example, in secondary aircraftstructures. Other embodiments of the present invention relate toradomes.

Some embodiments of the present invention relate to fiber glass strands.In some embodiments, a fiber glass strand of the present inventioncomprises a plurality of glass fibers comprising a glass compositionthat comprises the following components:

SiO₂ 60-68 weight percent; B₂O₃ 7-12 weight percent; Al₂O₃ 9-15 weightpercent; MgO 8-15 weight percent; CaO 0-4 weight percent; Li₂O 0-2weight percent; Na₂O 0-1 weight percent; K₂O 0-1 weight percent; Fe₂O₃0-1 weight percent; F₂ 0-1 weight percent; TiO₂ 0-2 weight percent; andother constituents 0-5 weight percent total.In some embodiments, the (Li₂O+Na₂O+K₂O) content can be less than 2weight percent and the MgO content can be at least twice the content ofCaO on a weight percent basis.

In some embodiments, a fiber glass strand of the present inventioncomprises a plurality of glass fibers comprising a glass compositionthat comprises the following components:

SiO₂ 53.5-77 weight percent; B₂O₃ 4.5-14.5 weight percent; Al₂O₃4.5-18.5 weight percent; MgO 4-12.5 weight percent; CaO 0-10.5 weightpercent; Li₂O 0-4 weight percent; Na₂O 0-2 weight percent; K₂O 0-1weight percent; Fe₂O₃ 0-1 weight percent; F₂ 0-2 weight percent; TiO₂0-2 weight percent; and other constituents 0-5 weight percent total.

In some embodiments, a fiber glass strand of the present inventioncomprises a glass composition comprising:

SiO₂ 60-68 weight percent; B₂O₃ 7-12 weight percent; Al₂O₃ 9-15 weightpercent; MgO 8-15 weight percent; CaO 0-4 weight percent; Li₂O >0-2weight percent; Na₂O 0-1 weight percent; K₂O 0-1 weight percent; Fe₂O₃0-1 weight percent; F₂ 0-1 weight percent; TiO₂ 0-2 weight percent; andother constituents 0-5 weight percent total;wherein the Li₂O content is greater than either the Na₂O content or theK₂O content.

A number of other glass compositions are disclosed herein as part of thepresent invention, and other embodiments of the present invention relateto fiber glass strands formed from such compositions.

In some embodiments, fiber glass strands formed from glass compositionsdescribed herein can exhibit desirable properties, such as improvedfiber strength, Young's modulus, failure strain, and/or linearcoefficient of thermal expansion, while also exhibiting relatively lowdensity. Fiber glass strands comprising other glass compositions asdisclosed herein may also exhibit one or more such desirable properties.

Fiber glass strands can comprise glass fibers of various diameters,depending on the desired application. In some embodiments, a fiber glassstrand of the present invention comprises at least one glass fiberhaving a diameter between about 5 and about 13 μm. In other embodiments,the at least one glass fiber has a diameter between about 5 and about 7μm.

In some embodiments, fiber glass strands of the present invention can beformed into rovings. Rovings can comprise assembled, multi-end, orsingle-end direct draw rovings. Rovings comprising fiber glass strandsof the present invention can comprise direct draw single-end rovingshaving various diameters and densities, depending on the desiredapplication. In some embodiments, a roving comprising fiber glassstrands of the present invention exhibits a density up to about 112yds/lb.

Some embodiments of the present invention relate to yarns comprising atleast one fiber glass strand as disclosed herein. In some embodiments, ayarn of the present invention comprises at least one fiber glass strandcomprising a glass composition that comprises 60-68 weight percent SiO₂,7-12 weight percent B₂O₃, 9-15 weight percent Al₂O₃, 8-15 weight percentMgO, 0-4 weight percent CaO, 0-2 weight percent Li₂O, 0-1 weight percentNa₂O, 0-1 weight percent K₂O, 0-1 weight percent F₂O₃, 0-1 weightpercent F₂, 0-2 weight percent TiO₂, and 0-5 weight percent total otherconstituents. A yarn, in some embodiments, comprises at least one fiberglass strand comprising a glass composition that comprises 53.5-77weight percent SiO₂, 4.5-14.5 weight percent B₂O₃, 4.5-18.5 weightpercent Al₂O₃, 4-12.5 weight percent MgO, 0-10.5 weight percent CaO, 0-4weight percent Li₂O, 0-2 weight percent Na₂O, 0-1 weight percent K₂O,0-1 weight percent F₂O₃, 0-2 weight percent F₂, 0-2 weight percent TiO₂,and 0-5 weight percent total other constituents. In other embodiments, ayarn of the present invention can comprise at least one fiber glassstrand comprising one of the other glass compositions disclosed hereinas part of the present invention.

In some embodiments, a yarn of the present invention comprises at leastone fiber glass strand as disclosed herein, wherein the at least onefiber glass strand is at least partially coated with a sizingcomposition. In some embodiments, the sizing composition is compatiblewith a thermosetting polymeric resin. In other embodiments, the sizingcomposition can comprise a starch-oil sizing composition.

Yarns can have various linear mass densities, depending on the desiredapplication. In some embodiments, a yarn of the present invention has alinear mass density from of 5,000 yds/lb to about 10,000 yds/lb.

Yarns can have various twist levels and directions, depending on thedesired application. In some embodiments, a yarn of the presentinvention has a twist in the z direction of about 0.5 to about 2 turnsper inch. In other embodiments, a yarn of the present invention has atwist in the z direction of about 0.7 turns per inch.

Yarns can be made from one or more strands that are twisted togetherand/or plied, depending on the desired application. Yarns can be madefrom one or more strands that are twisted together but not plied; suchyarns are known as “singles.” Yarns of the present invention can be madefrom one or more strands that are twisted together but not plied. Insome embodiments, yarns of the present invention comprise 1-4 strandstwisted together. In other embodiments, yarns of the present inventioncomprise 1 twisted strand.

Some embodiments of yarns comprising glass compositions of the presentinvention can demonstrate improved break load retention following heatcleaning and finishing as compared to yarns made from conventional glasscompositions.

Some embodiments of the present invention relate to fabrics comprisingat least one fiber glass strand. In some embodiments, a fabric comprisesat least one fiber glass strand comprising a glass composition thatcomprises 60-68 weight percent SiO₂, 7-12 weight percent B₂O₃, 9-15weight percent Al₂O₃, 8-15 weight percent MgO, 0-4 weight percent CaO,0-2 weight percent Li₂O, 0-1 weight percent Na₂O, 0-1 weight percentK₂O, 0-1 weight percent F₂O₃, 0-1 weight percent F₂, 0-2 weight percentTiO₂, and 0-5 weight percent total other constituents. A fabric, in someembodiments, comprises at least one fiber glass strand comprising aglass composition that comprises 53.5-77 weight percent SiO₂, 4.5-14.5weight percent B₂O₃, 4.5-18.5 weight percent Al₂O₃, 4-12.5 weightpercent MgO, 0-10.5 weight percent CaO, 0-4 weight percent Li₂O, 0-2weight percent Na₂O, 0-1 weight percent K₂O, 0-1 weight percent F₂O₃,0-2 weight percent F₂, 0-2 weight percent TiO₂, and 0-5 weight percenttotal other constituents. In other embodiments, a fabric of the presentinvention can comprise at least one fiber glass strand comprising one ofthe other glass compositions disclosed herein as part of the presentinvention. In some embodiments, a fabric of the present inventioncomprises a yarn as disclosed herein. Fabrics of the present invention,in some embodiments, can comprise at least one fill yarn comprising atleast one fiber glass strand as disclosed herein. Fabrics of the presentinvention, in some embodiments, can comprise at least one warp yarncomprising at least one fiber glass strand as disclosed herein. In someembodiments, a fabric of the present invention comprises at least onefill yarn comprising at least one fiber glass strand as disclosed hereinand at least one warp yarn comprising at least one fiber glass strand asdisclosed herein.

In some embodiments of the present invention comprising a fabric, theglass fiber fabric is a fabric woven in accordance with industrialfabric style no. 7781. In other embodiments, the fabric comprises aplain weave fabric, a twill fabric, a crowfoot fabric, a satin weavefabric, a stitch bonded fabric (also known as a non crimp fabric), or a“three-dimensional” woven fabric.

Some embodiments of the present invention relate to composites. In someembodiments, a composite of the present invention comprises a polymericresin and a plurality of glass fibers disposed in the polymeric resin,wherein at least one of the plurality of glass fibers comprises a glasscomposition that comprises the following components: 60-68 weightpercent SiO₂, 7-12 weight percent B₂O₃, 9-15 weight percent Al₂O₃, 8-15weight percent MgO, 0-4 weight percent CaO, 0-2 weight percent Li₂O, 0-1weight percent Na₂O, 0-1 weight percent K₂O, 0-1 weight percent F₂O₃,0-1 weight percent F₂, 0-2 weight percent TiO₂, and 0-5 weight percenttotal other constituents. A composite of the present invention, in someembodiments, comprises a polymeric resin and a plurality of glass fibersdisposed in the polymeric resin, wherein at least one of the pluralityof glass fibers comprises a glass composition that comprises thefollowing components: 53.5-77 weight percent SiO₂, 4.5-14.5 weightpercent B₂O₃, 4.5-18.5 weight percent Al₂O₃, 4-12.5 weight percent MgO,0-10.5 weight percent CaO, 0-4 weight percent Li₂O, 0-2 weight percentNa₂O, 0-1 weight percent K₂O, 0-1 weight percent F₂O₃, 0-2 weightpercent F₂, 0-2 weight percent TiO₂, and 0-5 weight percent total otherconstituents. In other embodiments, a composite of the present inventioncan comprise a polymeric resin and a plurality of glass fibers disposedin the polymeric resin, wherein at least one of the plurality of glassfibers was formed from one of the other glass compositions disclosedherein as part of the present invention. In some embodiments, acomposite of the present invention comprises a polymeric resin and atleast one fiber glass strand as disclosed herein disposed in thepolymeric resin. In some embodiments, a composite of the presentinvention comprises a polymeric resin and at least a portion of a rovingcomprising at least one fiber glass strand as disclosed herein disposedin the polymeric resin. In other embodiments, a composite of the presentinvention comprises a polymeric resin and at least one yarn as disclosedherein disposed in the polymeric resin. In still other embodiments, acomposite of the present invention comprises a polymeric resin and atleast one fabric as disclosed herein disposed in the polymeric resin. Insome embodiments, a composite of the present invention comprises atleast one fill yarn comprising at least one fiber glass strand asdisclosed herein and at least one warp yarn comprising at least onefiber glass strand as disclosed herein.

Composites of the present invention can comprise various polymericresins, depending on the desired properties and applications. In someembodiments of the present invention comprising a composite, thepolymeric resin comprises an epoxy resin. In other embodiments of thepresent invention comprising a composite, the polymeric resin cancomprise polyethylene, polypropylene, polyamide, polyimide, polybutyleneterephthalate, polycarbonate, thermoplastic polyurethane, phenolic,polyester, vinyl ester, polydicyclopentadiene, polyphenylene sulfide,polyether ether ketone, cyanate esters, bis-maleimides, and thermosetpolyurethane resins.

Some embodiments of the present invention relate to aerospacecomposites. In some embodiments, an aerospace composite of the presentinvention exhibits properties desirable for use in aerospaceapplications, such as high modulus, high failure-to-strain, and/or lowdensity. The low density of some aerospace composites of the presentinvention can make such composites especially desirable for use inaerospace applications in which reducing weight is important. Aerospacecomposites of the present invention can also cost less than othercomposites used in aerospace applications.

In some embodiments, an aerospace composite of the present inventioncomprises a polymeric resin and a plurality of glass fibers disposed inthe polymeric resin, wherein at least one of the plurality of glassfibers comprises a glass composition that comprises the followingcomponents: 60-68 weight percent SiO₂, 7-12 weight percent B₂O₃, 9-15weight percent Al₂O₃, 8-15 weight percent MgO, 0-4 weight percent CaO,0-2 weight percent Li₂O, 0-1 weight percent Na₂O, 0-1 weight percentK₂O, 0-1 weight percent F₂O₃, 0-1 weight percent F₂, 0-2 weight percentTiO₂, and 0-5 weight percent total other constituents. An aerospacecomposite of the present invention, in some embodiments, comprises apolymeric resin and a plurality of glass fibers disposed in thepolymeric resin, wherein at least one of the plurality of glass fiberscomprises a glass composition that comprises the following components:53.5-77 weight percent SiO₂, 4.5-14.5 weight percent B₂O₃, 4.5-18.5weight percent Al₂O₃, 4-12.5 weight percent MgO, 0-10.5 weight percentCaO, 0-4 weight percent Li₂O, 0-2 weight percent Na₂O, 0-1 weightpercent K₂O, 0-1 weight percent F₂O₃, 0-2 weight percent F₂, 0-2 weightpercent TiO₂, and 0-5 weight percent total other constituents. In otherembodiments, an aerospace composite of the present invention cancomprise a polymeric resin and a plurality of glass fibers disposed inthe polymeric resin, wherein at least one of the plurality of glassfibers was formed from one of the other glass compositions disclosedherein as part of the present invention.

In some embodiments, an aerospace composite of the present inventioncomprises a polymeric resin and at least one fiber glass strand asdisclosed herein disposed in the polymeric resin. In some embodiments,an aerospace composite of the present invention comprises a polymericresin and at least a portion of a roving comprising at least one fiberglass strand as disclosed herein disposed in the polymeric resin. Inother embodiments, an aerospace composite of the present inventioncomprises a polymeric resin and at least one yarn as disclosed hereindisposed in the polymeric resin. In still other embodiments, anaerospace composite of the present invention comprises a polymeric resinand at least one fabric as disclosed herein disposed in the polymericresin. In some embodiments, an aerospace composite of the presentinvention comprises at least one fill yarn comprising at least one fiberglass strand as disclosed herein and at least one warp yarn comprisingat least one fiber glass strand as disclosed herein.

Aerospace composites of the present invention can comprise variouspolymeric resins, depending on the desired properties and applications.In some embodiments of the present invention comprising an aerospacecomposite, the polymeric resin comprises an epoxy resin. In otherembodiments of the present invention comprising an aerospace composite,the polymeric resin can comprise polyethylene, polypropylene, polyamide,polyimide, polybutylene terephthalate, polycarbonate, thermoplasticpolyurethane, phenolic, polyester, vinyl ester, polydicyclopentadiene,polyphenylene sulfide, polyether ether ketone, cyanate esters,bis-maleimides, and thermoset polyurethane resins. Examples of parts inwhich aerospace composites of the present invention might be used caninclude, but are not limited to floor panels, overhead bins, galleys,seat back, and other internal compartments that are potentially prone toimpact, as well as external components such as helicopter rotor blades.

Some embodiments of the present invention relate to aviation composites.In some embodiments, an aviation composite of the present inventionexhibits properties desirable for use in aviation applications, such ashigh modulus, high failure-to-strain, and/or low density. The highfailure-to-strain of some aviation composites of the present inventioncan make such composites especially desirable for use in aviationapplications in which high impact resistance is important, such asaircraft interior applications. In some embodiments, aviation compositesof the present invention can demonstrate increased impact performance ascompared to composites formed from E-glass fabrics. Aviation compositesof the present invention can also cost less than other composites usedin aviation applications. Aviation composites of the present inventioncan be suitable for use in aircraft interiors (including, among otherthings, luggage storage bins, seats, and floors).

In some embodiments, an aviation composite of the present inventioncomprises a polymeric resin and a plurality of glass fibers disposed inthe polymeric resin, wherein at least one of the plurality of glassfibers comprises a glass composition that comprises the followingcomponents: 60-68 weight percent SiO₂, 7-12 weight percent B₂O₃, 9-15weight percent Al₂O₃, 8-15 weight percent MgO, 0-4 weight percent CaO,0-2 weight percent Li₂O, 0-1 weight percent Na₂O, 0-1 weight percentK₂O, 0-1 weight percent F₂O₃, 0-1 weight percent F₂, 0-2 weight percentTiO₂, and 0-5 weight percent total other constituents. An aviationcomposite of the present invention, in some embodiments, comprises apolymeric resin and a plurality of glass fibers disposed in thepolymeric resin, wherein at least one of the plurality of glass fiberscomprises a glass composition that comprises the following components:53.5-77 weight percent SiO₂, 4.5-14.5 weight percent B₂O₃, 4.5-18.5weight percent Al₂O₃, 4-12.5 weight percent MgO, 0-10.5 weight percentCaO, 0-4 weight percent Li₂O, 0-2 weight percent Na₂O, 0-1 weightpercent K₂O, 0-1 weight percent F₂O₃, 0-2 weight percent F₂, 0-2 weightpercent TiO₂, and 0-5 weight percent total other constituents. In otherembodiments, an aviation composite of the present invention can comprisea polymeric resin and a plurality of glass fibers disposed in thepolymeric resin, wherein at least one of the plurality of glass fiberswas formed from one of the other glass compositions disclosed herein aspart of the present invention.

In some embodiments, an aviation composite of the present inventioncomprises a polymeric resin and at least one fiber glass strand asdisclosed herein disposed in the polymeric resin. In some embodiments,an aviation composite of the present invention comprises a polymericresin and at least a portion of a roving comprising at least one fiberglass strand as disclosed herein disposed in the polymeric resin. Inother embodiments, an aviation composite of the present inventioncomprises a polymeric resin and at least one yarn as disclosed hereindisposed in the polymeric resin. In still other embodiments, an aviationcomposite of the present invention comprises a polymeric resin and atleast one fabric as disclosed herein disposed in the polymeric resin. Insome embodiments, an aviation composite of the present inventioncomprises at least one fill yarn comprising at least one fiber glassstrand as disclosed herein and at least one warp yarn comprising atleast one fiber glass strand as disclosed herein.

Aviation composites of the present invention can comprise variouspolymeric resins, depending on the desired properties and applications.In some embodiments of the present invention comprising an aviationcomposite, the polymeric resin comprises a phenolic resin. In otherembodiments of the present invention comprising an aviation composite,the polymeric resin can comprise epoxy, polyethylene, polypropylene,polyamide, polyimide, polybutylene terephthalate, polycarbonate,thermoplastic polyurethane, phenolic, polyester, vinyl ester,polydicyclopentadiene, polyphenylene sulfide, polyether ether ketone,cyanate esters, bis-maleimides, and thermoset polyurethane resins.Examples of parts in which aerospace composites of the present inventionmight be used can include, but are not limited to floor panels, overheadbins, galleys, seat back, and other internal compartments that arepotentially prone to impact, as well as external components such ashelicopter rotor blades.

Some embodiments of the present invention relate to composites that canbe used in wind energy applications. In some embodiments, a composite ofthe present invention suitable for use in wind energy applicationsexhibits properties desirable for use in wind energy applications, suchas high modulus/high failure-to-strain and low density. Composites ofthe present invention suitable for use in wind energy applications canalso cost less than other composites used in wind energy applications.Composites of the present invention can be suitable for use in windturbine blades, particularly long wind turbine blades that are lighterweight but still strong compared to other long wind turbine blades.

In some embodiments, a composite of the present invention suitable foruse in wind energy applications comprises a polymeric resin and aplurality of glass fibers disposed in the polymeric resin, wherein atleast one of the plurality of glass fibers comprises a glass compositionthat comprises the following components: 60-68 weight percent SiO₂, 7-12weight percent B₂O₃, 9-15 weight percent Al₂O₃, 8-15 weight percent MgO,0-4 weight percent CaO, 0-2 weight percent Li₂O, 0-1 weight percentNa₂O, 0-1 weight percent K₂O, 0-1 weight percent F₂O₃, 0-1 weightpercent F₂, 0-2 weight percent TiO₂, and 0-5 weight percent total otherconstituents. A composite of the present invention suitable for use inwind energy applications, in some embodiments, comprises a polymericresin and a plurality of glass fibers disposed in the polymeric resin,wherein at least one of the plurality of glass fibers comprises a glasscomposition that comprises the following components: 53.5-77 weightpercent SiO₂, 4.5-14.5 weight percent B₂O₃, 4.5-18.5 weight percentAl₂O₃, 4-12.5 weight percent MgO, 0-10.5 weight percent CaO, 0-4 weightpercent Li₂O, 0-2 weight percent Na₂O, 0-1 weight percent K₂O, 0-1weight percent F₂O₃, 0-2 weight percent F₂, 0-2 weight percent TiO₂, and0-5 weight percent total other constituents. In other embodiments, anaviation composite of the present invention can comprise a polymericresin and a plurality of glass fibers disposed in the polymeric resin,wherein at least one of the plurality of glass fibers was formed fromone of the other glass compositions disclosed herein as part of thepresent invention.

In some embodiments, a composite of the present invention suitable foruse in wind energy applications comprises a polymeric resin and at leastone fiber glass strand as disclosed herein disposed in the polymericresin. In some embodiments, a composite of the present inventionsuitable for use in wind energy applications comprises a polymeric resinand at least a portion of a roving comprising at least one fiber glassstrand as disclosed herein disposed in the polymeric resin. In otherembodiments, a composite of the present invention suitable for use inwind energy applications comprises a polymeric resin and at least oneyarn as disclosed herein disposed in the polymeric resin. In still otherembodiments, a composite of the present invention suitable for use inwind energy applications comprises a polymeric resin and at least onefabric as disclosed herein disposed in the polymeric resin. In someembodiments, a composite of the present invention suitable for use inwind energy applications comprises at least one fill yarn comprising atleast one fiber glass strand as disclosed herein and at least one warpyarn comprising at least one fiber glass strand as disclosed herein.

Composites of the present invention suitable for use in wind energyapplications can comprise various polymeric resins, depending on thedesired properties and applications. In some embodiments of the presentinvention comprising a composite suitable for use in wind energyapplications, the polymeric resin comprises an epoxy resin. In otherembodiments of the present invention comprising a composite suitable foruse in wind energy applications, the polymeric resin can comprisepolyester resins, vinyl esters, thermoset polyurethanes, orpolydicyclopentadiene resins.

Some embodiments of the present invention relate to laminates. Laminatesof the present invention can comprise a plurality of sheet-like layerscombined to form a laminate. In some embodiments, a laminate of thepresent invention comprises at least one layer comprising a composite asdescribed herein. In some embodiments, a laminate of the presentinvention comprises at least one layer comprising a composite comprisinga polymeric resin and a plurality of glass fibers disposed in thepolymeric resin, wherein at least one of the plurality of glass fiberscomprises a glass composition that comprises the following components:60-68 weight percent SiO₂, 7-12 weight percent B₂O₃, 9-15 weight percentAl₂O₃, 8-15 weight percent MgO, 0-4 weight percent CaO, 0-2 weightpercent Li₂O, 0-1 weight percent Na₂O, 0-1 weight percent K₂O, 0-1weight percent F₂O₃, 0-1 weight percent F₂, 0-2 weight percent TiO₂, and0-5 weight percent total other constituents. A laminate of the presentinvention, in some embodiments, comprises at least one layer comprisinga composite comprising a polymeric resin and a plurality of glass fibersdisposed in the polymeric resin, wherein at least one of the pluralityof glass fibers comprises a glass composition that comprises thefollowing components: 53.5-77 weight percent SiO₂, 4.5-14.5 weightpercent B₂O₃, 4.5-18.5 weight percent Al₂O₃, 4-12.5 weight percent MgO,0-10.5 weight percent CaO, 0-4 weight percent Li₂O, 0-2 weight percentNa₂O, 0-1 weight percent K₂O, 0-1 weight percent F₂O₃, 0-2 weightpercent F₂, 0-2 weight percent TiO₂, and 0-5 weight percent total otherconstituents. In other embodiments, a laminate of the present inventioncan comprise at least one layer comprising a composite comprising apolymeric resin and a plurality of glass fibers disposed in thepolymeric resin, wherein at least one of the plurality of glass fiberswas formed from one of the other glass compositions disclosed herein aspart of the present invention.

In some embodiments, a laminate of the present invention comprises acomposite comprising a polymeric resin and at least one fiber glassstrand as disclosed herein disposed in the polymeric resin. In someembodiments, a laminate of the present invention comprises a polymericresin and at least a portion of a roving comprising at least one fiberglass strand as disclosed herein disposed in the polymeric resin. Inother embodiments, a laminate of the present invention comprises acomposite comprising a polymeric resin and at least one yarn asdisclosed herein disposed in the polymeric resin. In still otherembodiments, a laminate of the present invention comprises a compositecomprising a polymeric resin and at least one fabric as disclosed hereindisposed in the polymeric resin. In some embodiments, a laminate of thepresent invention comprises at least one fill yarn comprising at leastone fiber glass strand as disclosed herein and at least one warp yarncomprising at least one fiber glass strand as disclosed herein.

Laminates of the present invention can comprise various polymericresins, depending on the desired properties and applications. In someembodiments of the present invention comprising a laminate, thepolymeric resin comprises an epoxy resin. In other embodiments of thepresent invention comprising a composite, the polymeric resin cancomprise polyethylene, polypropylene, polyamide, polyimide, polybutyleneterephthalate, polycarbonate, thermoplastic polyurethane, phenolic,polyester, vinyl ester, polydicyclopentadiene, polyphenylene sulfide,polyether ether ketone, cyanate esters, bis-maleimides, and thermosetpolyurethane resins.

Some embodiments of the present invention relate to prepregs. Prepregsof the present invention can comprise a polymeric resin and at least onefiber glass strand as disclosed herein. In some embodiments, a prepregof the present invention comprises a polymeric resin and a plurality ofglass fibers in contact with the polymeric resin, wherein at least oneof the plurality of glass fibers comprises a glass composition thatcomprises the following components: 60-68 weight percent SiO₂, 7-12weight percent B₂O₃, 9-15 weight percent Al₂O₃, 8-15 weight percent MgO,0-4 weight percent CaO, 0-2 weight percent Li₂O, 0-1 weight percentNa₂O, 0-1 weight percent K₂O, 0-1 weight percent F₂O₃, 0-1 weightpercent F₂, 0-2 weight percent TiO₂, and 0-5 weight percent total otherconstituents. A prepreg of the present invention, in some embodiments,comprises a polymeric resin and a plurality of glass fibers in contactwith the polymeric resin, wherein at least one of the plurality of glassfibers comprises a glass composition that comprises the followingcomponents: 53.5-77 weight percent SiO₂, 4.5-14.5 weight percent B₂O₃,4.5-18.5 weight percent Al₂O₃, 4-12.5 weight percent MgO, 0-10.5 weightpercent CaO, 0-4 weight percent Li₂O, 0-2 weight percent Na₂O, 0-1weight percent K₂O, 0-1 weight percent F₂O₃, 0-2 weight percent F₂, 0-2weight percent TiO₂, and 0-5 weight percent total other constituents. Inother embodiments, a prepreg of the present invention can comprise apolymeric resin and a plurality of glass fibers in contact with thepolymeric resin, wherein at least one of the plurality of glass fiberswas formed from one of the other glass compositions disclosed herein aspart of the present invention.

In some embodiments, a prepreg of the present invention comprises apolymeric resin and at least one fiber glass strand as disclosed hereinin contact with the polymeric resin. In some embodiments, a prepreg ofthe present invention comprises a polymeric resin and at least a portionof a roving comprising at least one fiber glass strand as disclosedherein disposed in the polymeric resin. In other embodiments, a prepregof the present invention comprises a polymeric resin and at least oneyarn as disclosed herein in contact with the polymeric resin. In stillother embodiments, a prepreg of the present invention comprises apolymeric resin and at least one fabric as disclosed herein in contactwith the polymeric resin. In some embodiments, a prepreg of the presentinvention comprises at least one fill yarn comprising at least one fiberglass strand as disclosed herein and at least one warp yarn comprisingat least one fiber glass strand as disclosed herein.

Prepregs of the present invention can comprise various polymeric resins,depending on the desired properties and applications. In someembodiments of the present invention comprising a prepreg, the polymericresin comprises an epoxy resin. In other embodiments of the presentinvention comprising a prepreg, the polymeric resin can comprisepolyethylene, polypropylene, polyamide, polyimide, polybutyleneterephthalate, polycarbonate, thermoplastic polyurethane, phenolic,polyester, vinyl ester, polydicyclopentadiene, polyphenylene sulfide,polyether ether ketone, cyanate esters, bis-maleimides, and thermosetpolyurethane resins.

Prepregs, in some embodiments of the present invention, can beincorporated into other products. For example, in some embodiments,prepregs of the present invention can be incorporated into a fiber-metallaminate. Incorporating a prepreg of the present invention into afiber-metal laminate can be advantageous because, in some embodiments,the prepreg can have excellent crack arresting properties and specificgravity relative to the metal sheets that might be used (e.g., analuminum alloy sheet). Several fiber-metal laminates, such as GLARE andARALL, are well-known, and prepregs of the present invention can readilybe incorporated into those structures. Fiber-metal laminates such asGLARE (“Glass Laminate Aluminum Reinforced Epoxy”) and ARALL (an aramidfiber-based fiber-metal laminate) were developed as lightweight fuselagematerials for aerospace applications with GLARE generally directedtowards fuselage applications and ARALL generally directed towards wingapplications. GLARE fiber-metal laminates are traditionally constructedby alternating layers of a fiber glass/epoxy prepreg (unidirectional orbiaxial) with pre-treated aluminum foil (i.e., 0.2-0.4 mm thick 2024 T3foil, etched using proprietary processes to enhance adhesion to thecomposite layers). These laminated structures can have wideapplicability in aircraft structures due to their excellent fatigueperformance, reduced corrosion rates, and slow crack propagationcharacteristics in the presence of stress risers (e.g., holes, rivets,edges). Such laminates are typically molded in an autoclave or pressunder heat and pressure. An example of a GLARE fiber-metal laminate canincorporate 3 layers of aluminum and 2 layers of biaxial composite andis sometimes referred to as a GLARE 3/2 laminates. Embodiments may alsoexist that incorporate 4 layers of aluminum and 3 layers of composite,or 5 layers of aluminum and 4 layers of composite.

Prepregs of the present invention can be substituted into such GLARE andARALL fiber-metal laminates (or other fiber-metal laminates) as areplacement for current fiber glass prepregs used in such products.Accordingly, a fiber-metal laminate can comprise a prepreg according tosome embodiments of the present invention, a first metal sheetadhesively secured to one surface of the prepreg, and a second metalsheet adhesively secured to a second surface of the prepreg, such thatthe prepreg is positioned between the two metal sheets. In someembodiments, multiple layers of prepregs can be incorporated in, forexample, a 3/2 arrangement (two prepreg layers between three metalsheets in a metal/prepreg/metal/prepreg/metal arrangement), a 4/3arrangement (three prepreg layers between four metal sheets in ametal/prepreg/metal/prepreg/metal/prepreg/metal arrangement), a 5/4arrangement (four prepreg layers between five metal sheets in ametal/prepreg/metal/prepreg/metal/prepreg/metal/prepreg/metalarrangement), or other arrangements. In some embodiments, the metalsheets can comprise aluminum or other metals typically used infiber-metal laminates. In some embodiments, the polymeric resin used inthe prepreg comprises epoxy. In some embodiments, the prepreg isadhesively secured to the metal sheets using a film adhesive for acontrolled bond line thickness as is known to those of skill in the art.In some embodiments, a separate adhesive is not require as the polymericresin (e.g., an epoxy) used in the prepreg can adhere the prepreg to themetal sheets.

Some embodiments of the present invention relate to radomes. Radomes areradar enclosures or structural shells that are typically built usingmaterials that provide a low dielectric constant to minimize signalreflections to/from the radar. High cost fibers such as quartz andaramid, as well as high strength fiber glass, have been usedsuccessfully in the production of radomes in combination with variousresin systems. In addition to the radar transparency requirements,materials for radomes preferably provide high stiffness/strength as wellas excellent durability characteristics to withstand environmental loads(wind, snow, rain, hail, fluctuating temperatures and UV degradation).Glass fibers according to some embodiments of the present invention canhave a dielectric constant of 5.3@1 MHz which, although higher thanquartz (−3.5), is lower than E-glass (6.3-6.6@1 MHz) and comparable toS-2 glass (5-5.4@1 MHz), making it a suitable glass fiber for use inradome applications.

In some embodiments, a radome of the present invention comprises apolymeric resin and a plurality of glass fibers disposed in thepolymeric resin, wherein at least one of the plurality of glass fiberscomprises a glass composition that comprises the following components:60-68 weight percent SiO₂, 7-12 weight percent B₂O₃, 9-15 weight percentAl₂O₃, 8-15 weight percent MgO, 0-4 weight percent CaO, 0-2 weightpercent Li₂O, 0-1 weight percent Na₂O, 0-1 weight percent K₂O, 0-1weight percent F₂O₃, 0-1 weight percent F₂, 0-2 weight percent TiO₂, and0-5 weight percent total other constituents. A radome of the presentinvention, in some embodiments, comprises a polymeric resin and aplurality of glass fibers disposed in the polymeric resin, wherein atleast one of the plurality of glass fibers comprises a glass compositionthat comprises the following components: 53.5-77 weight percent SiO₂,4.5-14.5 weight percent B₂O₃, 4.5-18.5 weight percent Al₂O₃, 4-12.5weight percent MgO, 0-10.5 weight percent CaO, 0-4 weight percent Li₂O,0-2 weight percent Na₂O, 0-1 weight percent K₂O, 0-1 weight percentF₂O₃, 0-2 weight percent F₂, 0-2 weight percent TiO₂, and 0-5 weightpercent total other constituents. In other embodiments, a radome of thepresent invention can comprise a polymeric resin and a plurality ofglass fibers disposed in the polymeric resin, wherein at least one ofthe plurality of glass fibers was formed from one of the other glasscompositions disclosed herein as part of the present invention.

In some embodiments, a radome of the present invention comprises a radarenclosure or structural shell comprising a polymeric resin and at leastone fiber glass strand as disclosed herein disposed in the polymericresin. In some embodiments, a radome of the present invention comprisesa polymeric resin and at least a portion of a roving comprising at leastone fiber glass strand as disclosed herein disposed in the polymericresin. In other embodiments, a radome of the present invention comprisesa polymeric resin and at least one yarn as disclosed herein disposed inthe polymeric resin. In still other embodiments, a radome of the presentinvention comprises a polymeric resin and at least one fabric asdisclosed herein disposed in the polymeric resin. In some embodiments, aradome of the present invention comprises at least one fill yarncomprising at least one fiber glass strand as disclosed herein and atleast one warp yarn comprising at least one fiber glass strand asdisclosed herein.

Radomes of the present invention can comprise various polymeric resins,depending on the desired properties and applications. In someembodiments of the present invention related to radomes, the polymericresin can comprise epoxy, phenolic, polyethylene, polypropylene,polyamide, polyimide, polybutylene terephthalate, polycarbonate,thermoplastic polyurethane, phenolic, polyester, vinyl ester,polydicyclopentadiene, polyphenylene sulfide, polyether ether ketone,cyanate esters, bis-maleimides, and thermoset polyurethane resins.

Glass fibers useful in the present invention can be made by any suitablemethod known to one of ordinary skill in the art, such as but notlimited to the method described above herein. Further, a primary sizingcomposition can be applied to the glass fibers using any suitable methodknown to one of ordinary skill in the art. In some embodiments, thesizing composition can be applied immediately after forming the glassfibers. The sizing composition can comprise any suitable sizingcomposition known to one of ordinary skill in the art for reinforcementapplications. In some embodiments, the sizing composition does notcomprise a starch-oil sizing composition. In some embodiments of thepresent invention comprising a sizing composition that does not comprisea starch-oil sizing composition, a sized glass fiber or glass fiberstrand need not be further treated with a slashing composition prior tousing the fiber or strand in weaving applications. In other embodimentscomprising a sizing composition that does not comprise a starch-oilsizing composition, a sized glass fiber or glass fiber strand mayoptionally be further treated with a slashing composition prior to usingthe fiber or strand in weaving applications. In some embodiments of thepresent invention comprising a primary sizing composition, the sizingcomposition can comprise a starch-oil sizing composition. In someembodiments of the present invention comprising a starch-oil sizingcomposition, the starch-oil sizing composition may later be removed froma fabric formed from at least one sized glass fiber or fiber glassstrand. In some embodiments, the starch-oil sizing may be removed from afabric using any suitable method known to one of ordinary skill in theart, such as but not limited to heat cleaning. In embodiments of thepresent invention comprising fabrics from which a starch-oil sizingcomposition has been removed, a fabric of the present invention mayfurther be treated with a finish coating.

Fiber glass strands of the present invention can be prepared by anysuitable method known to one of ordinary skill in the art. Glass fiberfabrics of the present invention can generally be made by any suitablemethod known to one of ordinary skill in the art, such as but notlimited to interweaving weft yarns (also referred to as “fill yarns”)into a plurality of warp yarns. Such interweaving can be accomplished bypositioning the warp yarns in a generally parallel, planar array on aloom, and thereafter weaving the weft yarns into the warp yarns bypassing the weft yarns over and under the warp yarns in a predeterminedrepetitive pattern. The pattern used depends upon the desired fabricstyle.

Warp yarns can generally be prepared using techniques known to those ofskill in the art. Warp yarns can be formed by attenuating a plurality ofmolten glass streams from a bushing or spinner. Thereafter, a sizingcomposition can be applied to the individual glass fibers and the fiberscan be gathered together to form a strand. The strands can besubsequently processed into yarns by transferring the strands to abobbin via a twist frame. During this transfer, the strands can be givena twist to aid in holding the bundle of fibers together. These twistedstrands can then be wound about the bobbin, and the bobbins can be usedin the weaving processes.

Positioning of the warp yarns on the loom can generally be done usingtechniques known to those of ordinary skill in the art. Positioning ofthe warp yarns on the loom can be done by way of a loom beam. A loombeam comprises a specified number of warp yarns (also referred to as“ends”) wound in an essentially parallel arrangement (also referred toas “warp sheet”) about a cylindrical core. Loom beam preparation cancomprise combining multiple yarn packages, each package comprising afraction of the number of ends required for the loom beam, into a singlepackage or loom beam. For example and although not limiting herein, a 50inch (127 cm) wide, a 7781 style fabric which utilizes a DE75 yarn inputtypically requires 2868 ends. However, conventional equipment forforming a loom beam does not allow for all of these ends to betransferred from bobbins to a single beam in one operation. Therefore,multiple beams comprising a fraction of the number of required ends,typically referred to as “section beams,” can be produced and thereaftercombined to form the loom beam. In a manner similar to a loom beam, asection beam can include a cylindrical core comprising a plurality ofessentially parallel warp yarns wound thereabout. While it will berecognized by one skilled in the art that the section beam can compriseany number of warp yarns required to form the final loom beam, generallythe number of ends contained on a section beam is limited by thecapacity of the warping creel. For a 7781 style fabric, four sectionbeams of 717 ends each of DE75 yarn are typically provided and whencombined offer the required 2868 ends for the warp sheet, as discussedabove.

Composites of the present invention can be prepared by any suitablemethod known to one of ordinary skill in the art, such as but notlimited to vacuum assisted resin infusion molding, extrusioncompounding, compression molding, resin transfer molding, filamentwinding, prepreg/autoclave curing, and pultrusion. Composites of thepresent invention can be prepared using such molding techniques as knownto those of ordinary skill in the art. In particular, embodiments ofcomposites of the present invention that incorporate woven fiber glassfabrics can be prepared using techniques known to those of skill in theart for preparation of such composites.

As an example, some composites of the present invention can be madeusing vacuum assisted compression molding, which technique is well-knownto those of skill in the art and described briefly below. As known tothose of skill in the art, with vacuum assisted compression molding, astack of pre-impregnated glass fabrics is placed within a press platen.In some embodiments of the present invention, the stack ofpre-impregnated glass fabrics can include one or more fabrics of thepresent invention as described herein that have been cut to a desiredsize and shape. Upon completion of the stacking operation for thecorresponding number of layers, the press is closed and the platens areconnected to a vacuum pump so that the upper platen compresses on thestack of fabrics until the desired pressure is achieved. The vacuum aidsin the evacuation of entrapped air within the stack and provides for areduced void content in the molded laminate. Following connection of theplatens to a vacuum pump, the temperature of the platens is thenincreased to accelerate the conversion rate of the resin (e.g., athermosetting resin) to a predetermined temperature setting particularto the resin utilized, and kept at that temperature and pressure settinguntil the laminate reaches full cure. At this point, the heat is turnedoff and the platens are cooled by water circulation until they reachroom temperature. The platens can then be opened, and the moldedlaminate can be removed from the press.

As another example, some composites of the present invention can be madeusing vacuum assisted resin infusion technology, as further describedherein. A stack of glass fiber fabrics of the present invention may becut to a desired size and placed on a silicone release treated glasstable. The stack may then be covered with a peel ply, fitted with a flowenhancing media, and vacuum bagged using nylon bagging film. Next, theso-called “lay up” may be subjected to a vacuum pressure of about 27inches Hg. Separately, the polymeric resin that is to be reinforced withthe fiber glass fabrics can be prepared using techniques known to thoseof skill in the art for that particular resin. For example, for somepolymeric resins, an appropriate resin (e.g., an amine-curable epoxyresin) may be mixed with an appropriate curing agent (e.g., an amine foran amine-curable epoxy resin) in the proportions recommended by theresin manufacturer or otherwise known to a person of ordinary skill inthe art. The combined resin may then be degassed in a vacuum chamber for30 minutes and infused through the fabric preform until substantiallycomplete wet out of the fabric stack is achieved. At this point, thetable may be covered with heated blankets (set to a temperature of about45-50° C.) for 24 hours. The resulting rigid composites may then bede-molded and post cured at about 250° F. for 4 hours in a programmableconvection oven. As is known to persons of ordinary skill in the art,however, various parameters such as degassing time, heating time, andpost curing conditions may vary based on the specific resin system used,and persons of ordinary skill in the art understand how to select suchparameters based on a particular resin system.

Laminates of the present invention can be prepared by any suitable meansknown to one of ordinary skill in the art, such as but not limited toinfusion.

Prepregs of the present invention can be prepared by any suitable meansknown to one of ordinary skill in the art, such as but not limited topassing fiber glass strands, rovings, or fabrics through a resin bath;using a solvent-based resin; or using a resin film.

Fiber-metal laminates of the present invention can be prepared by anysuitable means known to one of ordinary skill in the art using prepregsof the present invention.

Radomes of the present invention can be prepared by any suitable meansknown to one of ordinary skill in the art.

As noted above, some embodiments of the present invention can comprise aplurality of glass fibers. Glass fibers suitable for use in the presentinvention can have any appropriate diameter known to one of ordinaryskill in the art, depending on the desired application. Glass fiberssuitable for use in some embodiments of the present invention have adiameter of about 5 to about 13 μm. Glass fibers suitable for use inother embodiments of the present invention have a diameter of about 5-7μm.

In addition, glass fibers and glass fiber strands suitable for use inthe present invention can comprise a variety of glass compositions thatalso represent embodiments of the present invention. Some embodiments ofsuch glass fibers and fiber glass strands are set forth above and othersare described below. As noted above, one example of glass fiber or fiberglass strand suitable for use in some embodiments of the presentinvention comprises a glass composition comprising

SiO₂ 60-68 weight percent; B₂O₃ 7-12 weight percent; Al₂O₃ 9-15 weightpercent; MgO 8-15 weight percent; CaO 0-4 weight percent; Li₂O 0-2weight percent; Na₂O 0-1 weight percent; K₂O 0-1 weight percent; Fe₂O₃0-1 weight percent; F₂ 0-1 weight percent; TiO₂ 0-2 weight percent; andother constituents 0-5 weight percent total.

Another example of a glass fiber or fiber glass strand suitable for usein some embodiments of the present invention comprises a glasscomposition comprising

SiO₂ 60-68 weight percent; B₂O₃ 7-12 weight percent; Al₂O₃ 9-15 weightpercent; MgO 8-15 weight percent; CaO 0-4 weight percent; Li₂O >0-2weight percent; Na₂O 0-1 weight percent; K₂O 0-1 weight percent; Fe₂O₃0-1 weight percent; F₂ 0-1 weight percent; TiO₂ 0-2 weight percent; andother constituents 0-5 weight percent total;wherein the Li₂O content is greater than either the Na₂O content or theK₂O content. In other embodiments, the CaO content is 0-3 weightpercent. In still other embodiments, the CaO content is 0-2 weightpercent. In some embodiments, the CaO content is 0-1 weight percent. Insome embodiments of the present invention, the MgO content is 8-13weight percent. In other embodiments, the MgO content is 9-12 weightpercent. In some embodiments, the TiO₂ content is 0-1 weight percent. Insome embodiments, the B₂O₃ content is no more than 10 weight percent. Insome embodiments of the present invention, the Al₂O₃ content is 9-14weight percent. In other embodiments, the Al₂O₃ content is 10-13 weightpercent. In some embodiments, the (Li₂O+Na₂O+K₂O) content is less than 2weight percent. In some embodiments, the composition contains 0-1 weightpercent of BaO and 0-2 weight percent ZnO. In other embodiments, thecomposition contains essentially no BaO and essentially no ZnO. In someembodiments, other constituents, if any, are present in a total amountof 0-2 weight percent. In other embodiments, other constituents, if any,are present in a total amount of 0-1 weight percent. In someembodiments, the Li₂O content is 0.4-2.0 weight percent. In otherembodiments comprising a Li₂O content of 0.4-2.0 weight percent, theLi₂O content is greater than the (Na₂O+K₂O) content.

Another example of a glass fiber or fiber glass strand suitable for usein some embodiments of the present invention comprises a glasscomposition comprising

SiO₂ 60-68 weight percent; B₂O₃ 7-13 weight percent; Al₂O₃ 9-15 weightpercent; MgO 8-15 weight percent; CaO 0-4 weight percent; Li₂O 0-2weight percent; Na₂O 0-1 weight percent; K₂O 0-1 weight percent; Fe₂O₃0-1 weight percent; F₂ 0-1 weight percent; and TiO₂ 0-2 weight percent.In some embodiments, the glass compositions are characterized byrelatively low content of CaO, for example on the order of about 0-4weight percent. In yet other embodiments, the CaO content can be on theorder of about 0-3 weight percent. In some embodiments, the MgO contentis double that of the CaO content (on a weight percent basis). Someembodiments of the invention can have a MgO content greater than about6.0 weight percent, and in other embodiments the MgO content can begreater than about 7.0 weight percent. Some glass compositions suitablefor use in some embodiments of the present invention can becharacterized by the presence of less than 1.0 weight percent BaO. Inthose embodiments in which only trace impurity amounts of BaO arepresent, the BaO content can be characterized as being no more than 0.05weight percent.

Another example of a glass fiber or fiber glass strand suitable for usein some embodiments of the present invention comprises a glasscomposition comprising

SiO₂ 60-68 weight percent; B₂O₃ 7-12 weight percent; Al₂O₃ 9-15 weightpercent; MgO 8-15 weight percent; CaO 0-4 weight percent; Li₂O >0-2weight percent; Na₂O 0-1 weight percent; K₂O 0-1 weight percent; Fe₂O₃0-1 weight percent; F₂ 0-1 weight percent; TiO₂ 0-2 weight percent; andother constituents 0-5 weight percent total;wherein the Li₂O content is greater than either the Na₂O content or theK₂O content, and wherein the constituents are selected to provide aglass having a dielectric constant (D_(k)) less than 6.7 at 1 MHzfrequency. In other embodiments, the constituents are selected toprovide a glass having a dielectric constant (D_(k)) less than 6 at 1MHz frequency. In still other embodiments, the constituents are selectedto provide a glass having a dielectric constant (D_(k)) less than 5.8 at1 MHz frequency. In some embodiments, the constituents are selected toprovide a glass having a dielectric constant (D_(k)) less than 5.6 at 1MHz frequency.

The constituents of a glass composition suitable for use in someembodiments of the present invention can be selected based on a desiredforming temperature (defined as the temperature at which the viscosityis 1000 poise) and/or a desired liquidus temperature. In someembodiments, a glass fiber or fiber glass strand suitable for use in thepresent invention comprises a glass composition comprising

SiO₂ 60-68 weight percent; B₂O₃ 7-12 weight percent; Al₂O₃ 9-15 weightpercent; MgO 8-15 weight percent; CaO 0-4 weight percent; Li₂O >0-2weight percent; Na₂O 0-1 weight percent; K₂O 0-1 weight percent; Fe₂O₃0-1 weight percent; F₂ 0-1 weight percent; TiO₂ 0-2 weight percent; andother constituents 0-5 weight percent total;wherein the Li₂O content is greater than either the Na₂O content or theK₂O content, and wherein the constituents are selected to provide aforming temperature T_(F) at 1000 poise viscosity no greater than 1370°C. In other embodiments, the constituents are selected to provide aforming temperature T_(F) at 1000 poise viscosity no greater than 1320°C. In still other embodiments, the constituents are selected to providea forming temperature T_(F) at 1000 poise viscosity no greater than1300° C. In some embodiments, the constituents are selected to provide aforming temperature T_(F) at 1000 poise viscosity no greater than 1290°C. In some embodiments, the constituents are selected to provide aforming temperature T_(F) at 1000 poise viscosity no greater than 1370°C. and a liquidus temperature T_(L) at least 55° C. below the formingtemperature. In other embodiments, the constituents are selected toprovide a forming temperature T_(F) at 1000 poise viscosity no greaterthan 1320° C. and a liquidus temperature T_(L) at least 55° C. below theforming temperature. In still other embodiments, the constituents areselected to provide a forming temperature T_(F) at 1000 poise viscosityno greater than 1300° C. and a liquidus temperature T_(L) at least 55°C. below the forming temperature. In some embodiments, the constituentsare selected to provide a forming temperature T_(F) at 1000 poiseviscosity no greater than 1290° C. and a liquidus temperature T_(L) atleast 55° C. below the forming temperature.

Another example of a glass fiber or fiber glass strand suitable for usein some embodiments of the present invention comprises a glasscomposition comprising

B₂O₃ less than 12 weight percent; Al₂O₃ 9-15 weight percent; MgO 8-15weight percent; CaO 0-4 weight percent; SiO₂ 60-68 weight percent;Li₂O >0-2 weight percent; Na₂O 0-1 weight percent; K₂O 0-1 weightpercent; Fe₂O₃ 0-1 weight percent; F₂ 0-1 weight percent; and TiO₂ 0-2weight percent;wherein the glass exhibits a dielectric constant (D_(k)) less than 6.7and forming temperature (T_(F)) at 1000 poise viscosity no greater than1370° C. and wherein the Li₂O content is greater than either the Na₂Ocontent or the K₂O content. In some embodiments, the CaO content is 0-1weight percent.

Another example of a glass fiber or fiber glass strand suitable for usein some embodiments of the present invention comprises a glasscomposition comprising

SiO₂ 60-68 weight percent; B₂O₃ 7-12 weight percent; Al₂O₃ 9-15 weightpercent; MgO 8-15 weight percent; CaO 0-3 weight percent; Li₂O 0.4-2weight percent; Na₂O 0-1 weight percent; K₂O 0-1 weight percent; Fe₂O₃0-1 weight percent; F₂ 0-1 weight percent; and TiO₂ 0-2 weight percent;wherein the glass exhibits a dielectric constant (D_(k)) less than 5.9and forming temperature (T_(F)) at 1000 poise viscosity no greater than1300° C. and wherein the Li₂O content is greater than either the Na₂Ocontent or the K₂O content.

Another example of a glass fiber or fiber glass strand suitable for usein some embodiments of the present invention comprises a glasscomposition consisting essentially of

SiO₂ 60-68 weight percent; B₂O₃ 7-11 weight percent; Al₂O₃ 9-13 weightpercent; MgO 8-13 weight percent; CaO 0-3 weight percent; Li₂O 0.4-2weight percent; Na₂O 0-1 weight percent; K₂O 0-1 weight percent; (Na₂O +K₂O + Li₂O) 0-2 weight percent; Fe₂O₃ 0-1 weight percent; F₂ 0-1 weightpercent; and TiO₂ 0-2 weight percent;wherein the Li₂O content is greater than either the Na₂O content or theK₂O content. In some embodiments, the CaO content is 0-1 weight percent.In some embodiments comprising a CaO content of 0-1 weight percent, theB₂O₃ content is no more than 10 weight percent.

Another example of a glass fiber or fiber glass strand suitable for usein some embodiments of the present invention comprises a glasscomposition comprising

SiO₂ 60-68 weight percent; B₂O₃ 7-10 weight percent; Al₂O₃ 9-15 weightpercent; MgO 8-15 weight percent; CaO 0-4 weight percent; Li₂O >0-2weight percent; Na₂O 0-1 weight percent; K₂O 0-1 weight percent; Fe₂O₃0-1 weight percent; F₂ 0-1 weight percent; TiO₂ 0-2 weight percent; andother constituents 0-5 weight percent;wherein the Li₂O content is greater than either the Na₂O content or theK₂O content. In some embodiments, the constituents are selected toprovide a glass having a dielectric constant (D_(k)) less than 6.7 at 1MHz frequency. In other embodiments, the constituents are selected toprovide a glass having a dielectric constant (D_(k)) less than 6 at 1MHz frequency. In still other embodiments, the constituents are selectedto provide a glass having a dielectric constant (D_(k)) less than 5.8 at1 MHz frequency. In some embodiments, the constituents are selected toprovide a glass having a dielectric constant (D_(k)) less than 5.6 at 1MHz frequency.

Another example of a glass fiber or fiber glass strand suitable for usein some embodiments of the present invention comprises a glasscomposition comprising:

SiO₂ 53.5-77 weight percent; B₂O₃ 4.5-14.5 weight percent; Al₂O₃4.5-18.5 weight percent; MgO 4-12.5 weight percent; CaO 0-10.5 weightpercent; Li₂O 0-4 weight percent; Na₂O 0-2 weight percent; K₂O 0-1weight percent; Fe₂O₃ 0-1 weight percent; F₂ 0-2 weight percent; TiO₂0-2 weight percent; and other constituents 0-5 weight percent total.

Another example of a glass fiber or fiber glass strand suitable for usein some embodiments of the present invention comprises a glasscomposition comprising:

SiO₂ 60-77 weight percent; B₂O₃ 4.5-14.5 weight percent; Al₂O₃ 4.5-18.5weight percent; MgO 8-12.5 weight percent; CaO 0-4 weight percent; Li₂O0-3 weight percent; Na₂O 0-2 weight percent; K₂O 0-1 weight percent;Fe₂O₃ 0-1 weight percent; F₂ 0-2 weight percent; TiO₂ 0-2 weightpercent; and other constituents 0-5 weight percent total.

Another example of a glass fiber or fiber glass strand suitable for usein some embodiments of the present invention comprises a glasscomposition comprising:

SiO₂ at least 60 weight percent; B₂O₃ 5-11 weight percent; Al₂O₃ 5-18weight percent; MgO 5-12 weight percent; CaO 0-10 weight percent; Li₂O0-3 weight percent; Na₂O 0-2 weight percent; K₂O 0-1 weight percent;Fe₂O₃ 0-1 weight percent; F₂ 0-2 weight percent; TiO₂ 0-2 weightpercent; and other constituents 0-5 weight percent total.

Another example of a glass fiber or fiber glass strand suitable for usein some embodiments of the present invention comprises a glasscomposition comprising:

SiO₂ 60-68 weight percent; B₂O₃ 5-10 weight percent; Al₂O₃ 10-18 weightpercent; MgO 8-12 weight percent; CaO 0-4 weight percent; Li₂O 0-3weight percent; Na₂O 0-2 weight percent; K₂O 0-1 weight percent; Fe₂O₃0-1 weight percent; F₂ 0-2 weight percent; TiO₂ 0-2 weight percent; andother constituents 0-5 weight percent total.

Another example of a glass fiber or fiber glass strand suitable for usein some embodiments of the present invention comprises a glasscomposition comprising:

SiO₂ 62-68 weight percent; B₂O₃ 7-9 weight percent; Al₂O₃ 11-18 weightpercent; MgO 8-11 weight percent; CaO 1-2 weight percent; Li₂O 1-2weight percent; Na₂O 0-0.5 weight percent; K₂O 0-0.5 weight percent;Fe₂O₃ 0-0.5 weight percent; F₂ 0.5-1 weight percent; TiO₂ 0-1 weightpercent; and other constituents 0-5 weight percent total.

Another example of a glass fiber or fiber glass strand suitable for usein some embodiments of the present invention comprises a glasscomposition comprising:

SiO₂ 62-68 weight percent; B₂O₃ less than about 9 weight percent; Al₂O₃10-18 weight percent; MgO 8-12 weight percent; and CaO 0-4 weightpercent;wherein the glass exhibits a dielectric constant (D_(k)) less than 6.7and a forming temperature (T_(F)) at 1000 poise viscosity no greaterthan 1370° C.

Another example of a glass fiber or fiber glass strand suitable for usein some embodiments of the present invention comprises a glasscomposition comprising:

B₂O₃ less than 14 weight percent; Al₂O₃ 9-15 weight percent; MgO 8-15weight percent; CaO 0-4 weight percent; and SiO₂ 60-68 weight percent;wherein the glass exhibits a dielectric constant (D_(k)) less than 6.7and forming temperature (T_(F)) at 1000 poise viscosity no greater than1370° C.

Another example of a glass fiber or fiber glass strand suitable for usein some embodiments of the present invention comprises a glasscomposition comprising:

B₂O₃ less than 9 weight percent; Al₂O₃ 11-18 weight percent; MgO 8-11weight percent; CaO 1-2 weight percent; and SiO₂ 62-68 weight percent;wherein the glass exhibits a dielectric constant (D_(k)) less than 6.7and forming temperature (T_(F)) at 1000 poise viscosity no greater than1370° C.

Another example of a glass fiber or fiber glass strand suitable for usein some embodiments of the present invention comprises a glasscomposition comprising:

SiO₂ 60-68 weight percent; B₂O₃ 7-13 weight percent; Al₂O₃ 9-15 weightpercent; MgO 8-15 weight percent; CaO 0-3 weight percent; Li₂O 0.4-2weight percent; Na₂O 0-1 weight percent; K₂O 0-1 weight percent; Fe₂O₃0-1 weight percent; F₂ 0-1 weight percent; and TiO₂ 0-2 weight percent;wherein the glass exhibits a dielectric constant (D_(k)) less than 5.9and forming temperature (T_(F)) at 1000 poise viscosity no greater than1300° C.

Another example of a glass fiber or fiber glass strand suitable for usein some embodiments of the present invention comprises a glasscomposition comprising:

SiO₂ 60-68 weight percent; B₂O₃ 7-11 weight percent; Al₂O₃ 9-13 weightpercent; MgO 8-13 weight percent; CaO 0-3 weight percent; Li₂O 0.4-2weight percent; Na₂O 0-1 weight percent; K₂O 0-1 weight percent; (Na₂O +K₂O + Li₂O) 0-2 weight percent; Fe₂O₃ 0-1 weight percent; F₂ 0-1 weightpercent; and TiO₂ 0-2 weight percent.

In addition to or instead of the features of the invention describedabove, some embodiments of the glass compositions of the presentinvention can be utilized to provide glasses having dissipation factors(D_(f)) lower than standard electronic E-glass. In some embodiments,D_(F) may be no more than 0.0150 at 1 GHz, and in other embodiments nomore than 0.0100 at 1 GHz.

In some embodiments of glass compositions, D_(F) is no more than 0.007at 1 GHz, and in other embodiments no more than 0.003 at 1 GHz, and inyet other embodiments no more than 0.002 at 1 GHz.

In some embodiments, the glass compositions that can be used in glassfibers or fiber glass strands of the invention are characterized byrelatively low content of CaO, for example, on the order of about 0-4weight percent. In yet other embodiments, the CaO content can be on theorder of about 0-3 weight percent. In yet other embodiments, the CaOcontent can be on the order of about 0-2 weight percent. In general,minimizing the CaO content yields improvements in electrical properties,and the CaO content has been reduced to such low levels in someembodiments that it can be considered an optional constituent. In someother embodiments, the CaO content can be on the order of about 1-2weight percent.

On the other hand, the MgO content is relatively high for glasses ofthis type, wherein in some embodiments the MgO content is double that ofthe CaO content (on a weight percent basis). Some embodiments of theinvention can have MgO content greater than about 5.0 weight percent,and in other embodiments the MgO content can be greater than 8.0 weightpercent. In some embodiments, the compositions are characterized by aMgO content, for example, on the order of about 8-13 weight percent. Inyet other embodiments, the MgO content can be on the order of about 9-12weight percent. In some other embodiments, the MgO content can be on theorder of about 8-12 weight percent. In yet some other embodiments, theMgO content can be on the order of about 8-10 weight percent.

In some embodiments, the compositions that can be used in glass fibersor fiber glass strands of the invention are characterized by a (MgO+CaO)content, for example, that is less than 16 weight percent. In yet otherembodiments, the (MgO+CaO) content is less than 13 weight percent. Insome other embodiments, the (MgO+CaO) content is 7-16 weight percent. Inyet some other embodiments, the (MgO+CaO) content can be on the order ofabout 10-13 weight percent.

In yet some other embodiments, the compositions can be characterized bya ratio of (MgO+CaO)/(Li₂O+Na₂O+K₂O) content on the order of about 9.0.In certain embodiments, the ratio of Li₂O/(MgO+CaO) content can be onthe order of about 0-2.0. In yet some other embodiments, the ratio ofLi₂O/(MgO+CaO) content can be on the order of about 1-2.0. In certainembodiments, the ratio of Li₂O/(MgO+CaO) content can be on the order ofabout 1.0.

In some other embodiments, the (SiO₂+B₂O₃) content can be on the orderof 70-76 weight percent. In yet other embodiments, the (SiO₂+B₂O₃)content can be on the order of 70 weight percent. In other embodiments,the (SiO₂+B₂O₃) content can be on the order of 73 weight percent. Instill other embodiments, the ratio of the weight percent of Al₂O₃ to theweigh percent of B₂O₃ is on the order of 1-3. In some other embodiments,the ratio of the weight percent of Al₂O₃ to the weight percent of B₂O₃is on the order of 1.5-2.5. In certain embodiments, the SiO₂ content ison the order of 65-68 weight percent.

As noted above, some low D_(k) compositions of the prior art have thedisadvantage of requiring the inclusion of substantial amounts of BaO,and it can be noted that BaO is not required in some embodiments ofglass compositions of the present invention. Although the advantageouselectrical and manufacturing properties of the invention do not precludethe presence of BaO, the absence of deliberate inclusions of BaO can beconsidered an additional advantage of some embodiments of the presentinvention. Thus, embodiments of the present invention can becharacterized by the presence of less than 1.0 weight percent BaO. Inthose embodiments in which only trace impurity amounts are present, theBaO content can be characterized as being no more than 0.05 weightpercent.

The compositions that can be used in glass fibers or fiber glass strandsof the invention include B₂O₃ in amounts less that the prior artapproaches that rely upon high B₂O₃ to achieve low D_(k). This resultsin significant cost savings. In some embodiments the B₂O₃ content needbe no more than 13 weight percent, or no more than 12 weight percent.Some embodiments of the invention also fall within the ASTM definitionof electronic E-glass, i.e., no more than 10 weight percent B₂O₃.

In some embodiments, the compositions are characterized by a B₂O₃content, for example, on the order of about 5-11 weight percent. In someembodiments, the B₂O₃ content can be 6-11 weight percent. The B₂O₃content, in some embodiments, can be 6-9 weight percent. In someembodiments, the B₂O₃ content can be 5-10 weight percent. In some otherembodiments, the B₂O₃ content is not greater than 9 weight percent. Inyet some other embodiments, the B₂O₃ content is not greater than 8weight percent.

In some embodiments, the compositions that can be used in glass fibersor fiber glass strands of the present invention are characterized by aAl₂O₃ content, for example on the order of about 5-18 weight percent.The Al₂O₃ content, in some embodiments, can be 9-18 weight percent. Inyet other embodiments, the Al₂O₃ content is on the order of about 10-18weight percent. In some other embodiments, the Al₂O₃ content is on theorder of about 10-16 weight percent. In yet some other embodiments, theAl₂O₃ content is on the order of about 10-14 weight percent. In certainembodiments, the Al₂O₃ content is on the order of about 11-14 weightpercent.

In some embodiments, Li₂O is an optional constituent. In someembodiments, the compositions are characterized by a Li₂O content, forexample on the order of about 0.4-2.0 weight percent. In someembodiments, the Li₂O content is greater than the (Na₂O+K₂O) content. Insome embodiments, the (Li₂O+Na₂O+K₂O) content is not greater than 2weight percent. In some embodiments, the (Li₂O+Na₂O+K₂O) content is onthe order of about 1-2 weight percent.

In certain embodiments, the compositions of the invention arecharacterized by a TiO₂ content for example on the order of about 0-1weight percent.

In some embodiments of the compositions set forth above, theconstituents are proportioned so as to yield a glass having a dielectricconstant lower than that of standard E-glass. With reference to astandard electronic E-glass for comparison, this may be less than about6.7 at 1 MHz frequency. In other embodiments, the dielectric constant(D_(k)) may be less than 6 at 1 MHz frequency. In other embodiments, thedielectric constant (D_(k)) may be less than 5.8 at 1 MHz frequency.Further embodiments exhibit dielectric constants (D_(k)) less than 5.6or even lower at 1 MHz frequency. In other embodiments, the dielectricconstant (D_(k)) may be less than 5.4 at 1 MHz frequency. In yet otherembodiments, the dielectric constant (D_(k)) may be less than 5.2 at 1MHz frequency. In yet other embodiments, the dielectric constant (D_(k))may be less than 5.0 at 1 MHz frequency.

The compositions set forth above can also possess desirabletemperature-viscosity relationships conducive to practical commercialmanufacture of glass fibers. In general, lower temperatures are requiredfor making fibers compared to the D-glass type of composition in theprior art. The desirable characteristics may be expressed in a number ofways, and they may be attained by some embodiments of compositionsdescribed herein singly or in combination. For example, certain glasscompositions within the ranges set forth above can be made that exhibitforming temperatures (T_(F)) at 1000 poise viscosity no greater than1370° C. The T_(F) of some embodiments are no greater than 1320° C., orno greater than 1300° C., or no greater than 1290° C., or no greaterthan 1260° C., or no greater than 1250° C. These compositions can alsoencompass glasses in which the difference between the formingtemperature and the liquidus temperature (T_(L)) is positive, and insome embodiments the forming temperature is at least 55° C. greater thanthe liquidus temperature, which is advantageous for commercialmanufacturing of fibers from these glass compositions.

In general, minimizing alkali oxide content of the glass compositionsused to form the glass fibers or fiber glass strands can assist inlowering D_(k). In those embodiments in which it is desired to optimizereduction of D_(k) the total alkali oxide content may be no more than 2weight percent of the glass composition. In some embodiments, it hasbeen found that minimizing Na₂O and K₂O are more effective in thisregard than Li₂O. The presence of alkali oxides generally results inlower forming temperatures. Therefore, in those embodiments of theinvention in which providing relatively low forming temperatures is apriority, Li₂O is included in significant amounts, e.g. at least 0.4weight percent. For this purpose, in some embodiments the Li₂O contentis greater than either the Na₂O or K₂O contents, and in otherembodiments the Li₂O content is greater than the sum of the Na₂O and K₂Ocontents, in some embodiments greater by a factor of two or more.

One advantageous aspect in some of the embodiments is reliance uponconstituents that are conventional in the fiber glass industry andavoidance of substantial amounts of constituents whose raw materialsources are costly. For this aspect, constituents in addition to thoseexplicitly set forth in the compositional definition of the glasses ofthe present invention may be included even though not required, but intotal amounts no greater than 5 weight percent. These optionalconstituents include melting aids, fining aids, colorants, traceimpurities and other additives known to those of skill in glassmakingRelative to some prior art low D_(k) glasses, no BaO is required in thecompositions of the present invention, but inclusion of minor amounts ofBaO (e.g., up to about 1 weight percent) would not be precluded.Likewise, major amounts of ZnO are not required in the presentinvention, but in some embodiments minor amounts (e.g., up to about 2.0weight percent) may be included. In those embodiments of the inventionin which optional constituents are minimized, the total of optionalconstituents is no more than 2 weight percent, or no more than 1 weightpercent. Alternatively, some embodiments of the invention can be said toconsist essentially of the named constituents.

The choice of batch ingredients and their cost are significantlydependent upon their purity requirements. Typical commercialingredients, such as for E-glass making, contain impurities of Na₂O,K₂O, Fe₂O₃ or FeO, SrO, F₂, TiO₂, SO₃, etc. in various chemical forms. Amajority of the cations from these impurities would increase the D_(k)of the glasses by forming nonbridging oxygens with SiO₂ and/or B₂O₃ inthe glass.

Sulfate (expressed as SO₃) may also be present as a refining agent.Small amounts of impurities may also be present from raw materials orfrom contamination during the melting processes, such as SrO, BaO, Cl₂,P₂O₅, Cr₂O₃, or NiO (not limited to these particular chemical forms).Other refining agents and/or processing aids may also be present such asAs₂O₃, MnO, MnO₂, Sb₂O₃, or SnO₂, (not limited to these particularchemical forms). These impurities and refining agents, when present, areeach typically present in amounts less than 0.5% by weight of the totalglass composition. Optionally, elements from rare earth group of thePeriodic Table of the Elements may be added to compositions of thepresent invention, including atomic numbers 21 (Sc), 39 (Y), and 57 (La)through 71 (Lu). These may serve as either processing aids or to improvethe electrical, physical (thermal and optical), mechanical, and chemicalproperties of the glasses. The rare earth additives may be included withregard for the original chemical forms and oxidization states. Addingrare earth elements is considered optional, particularly in thoseembodiments of the present invention having the objective of minimizingraw material cost, because they would increase batch costs even at lowconcentrations. In any case, their costs would typically dictate thatthe rare earth components (measured as oxides), when included, bepresent in amounts no greater than about 0.1-1.0% by weight of the totalglass composition.

Glass fibers, fiber glass strands, and other products incorporating suchfibers or strands can exhibit desirable mechanical properties in someembodiments of the present invention, particularly as compared toE-glass fibers, fiber glass strands formed from E-glass, and relatedproducts. For example, some embodiments of glass fibers of the presentinvention can have relatively high specific strength or relatively highspecific modulus, particularly, when compared to E-glass fibers.Specific strength refers to the tensile strength in N/m² divided by thespecific weight in N/m³. Specific modulus refers to the Young's modulusin N/m² divided by the specific weight in N/m³. Glass fibers havingrelatively high specific strength and/or relatively high specificmodulus may be desirable in applications where there is a desire toincrease mechanical properties or product performance while reducing theoverall weight of the composite. Examples of such composites are setforth above and include, for example, aerospace or aviation applications(e.g., interior floors of planes), wind energy applications (e.g.,windmill blades), fiber-metal laminate applications, and others. Asanother example of a mechanical property, some embodiments of fiberglass strands of the present invention in the form of rovings canexhibit increased tensile strengths (e.g., on the order of 400-430 ksiin some embodiments per ASTM D2343) as compared to rovings incorporatingE-glass fiber glass strands (e.g., on the order of 350-400 ksi per ASTMD2343).

As is known in the art, after formation, glass fibers are typically atleast partially coated with a sizing composition. In general, glassfibers used to form fiber glass strands, fabrics, composites, laminates,and prepregs of the present invention will be at least partially coatedwith a sizing composition. One skilled in the art may choose one of manycommercially available sizing compositions for the glass fibers basedupon a number of factors including, for example, performance propertiesof the sizing compositions, desired flexibility of the resulting fabric,cost, and other factors. Non-limiting examples of commercially availablesizing compositions that can be used in some embodiments of the presentinvention include sizing compositions often used on single-end rovings,such as Hybon 2026, Hybon 2002, Hybon 1383, Hybon 2006, Hybon 2022,Hybon 2032, Hybon 2016, and Hybon 1062, as well as sizing compositionsoften used on yarns, such as 1383, 611, 900, 610, 695, and 690, each ofwhich refer to sizing compositions for products commercially availablefrom PPG Industries, Inc.

As noted above, some embodiments of the present invention can comprise afabric. Any suitable fabric design known to one of ordinary skill in theart for reinforcement applications can be used. Suitable fabrics caninclude fabrics produced using standard textile equipment (e.g., rapier,projectile, or air jet looms). Non-limiting examples of such fabricsinclude plain weaves, twill, crowfoot, and satin weaves. Stitch bondedor non-crimp fabrics can also be used in some embodiments of the presentinvention. Such fabrics can include, for example, unidirectional,biaxial and triaxial non-crimp fabrics. In addition, 3D woven fabricscan also be used in some embodiments of the present invention. Suchfabrics can be produced using multi-layer warp ends with shedding,either with the use of a dobby or a jacquard head.

As noted above, composites of the present invention can comprise warpand weft yarns. Any suitable warp and weft yarns known to one ofordinary skill in the art for reinforcement applications may be used. Insome embodiments, for example, warp yarns can comprise G75 yarn, DE75yarn, DE150 yarn, and/or G150 yarn.

As noted above, composites of the present invention can comprise apolymeric resin, in some embodiments. A variety of polymeric resins canbe used. Polymeric resins that are known to be useful in reinforcementapplications can be particularly useful in some embodiments. In someembodiments, the polymeric resin can comprise a thermoset resin.Thermoset resin systems useful in some embodiments of the presentinvention can include but are not limited to epoxy resin systems,phenolic based resins, polyesters, vinyl esters, thermosetpolyurethanes, polydicyclopentadiene (pDCPD) resins, cyanate esters, andbis-maleimides. In some embodiments, the polymeric resin can comprise anepoxy resin. In other embodiments, the polymeric resin can comprise athermoplastic resin. Thermoplastic polymers useful in some embodimentsof the present invention include but are not limited to polyethylene,polypropylene, polyamides (including Nylon), polybutylene terephthalate,polycarbonate, thermoplastic polyurethanes (TPU), polyphenylenesulfides, and polyether ether keteone (PEEK). Non-limiting examples ofcommercially available polymeric resins useful in some embodiments ofthe present invention include EPIKOTE Resin MGS® RIMR 135 epoxy withEpikure MGS RIMH 1366 curing agent (available from Momentive SpecialtyChemicals Inc. of Columbus, Ohio), Applied Poleramic MMFCS2 epoxy(available from Applied Poleramic, Inc., Benicia, Calif.), and EP255modified epoxy (available from Barrday Composite Solutions, Millbury,Mass.).

EXAMPLES

Some exemplary embodiments of the present invention will now beillustrated in the following specific, non-limiting examples.

Example 1

Some properties of a glass composition useful in some embodiments of thepresent invention were measured under controlled processing conditionsusing conventional testing methods known to those of ordinary skill inthe art. Some measured properties are listed in Table 1. Properties ofstandard E-glass and commercial NE-glass are included for reference. Theproperties listed for commercial NE-glass come from the literature. Thedata in Table 1 indicate that glass fibers suitable for use in thepresent invention exhibit improved thermal, chemical, and mechanicalstability compared to E-glass. Compared to NE-fibers, glass fiberssuitable for use in the present invention are 30% stronger and 25%stiffer. As measured by x-ray fluorescence spectroscopy, the glassfibers of Sample 1 in Table 1 comprised a glass composition comprising

SiO₂ 63.02 ± 0.25 weight percent; B₂O₃ 9.39 ± 0.15 weight percent; Al₂O₃11.60 ± 0.10 weight percent; MgO 11.06 ± 0.15 weight percent; CaO 2.54 ±0.10 weight percent; Na₂O 0.38 ± 0.02 weight percent; K₂O 0.12 ± 0.01weight percent; Fe₂O₃ 0.25 ± 0.05 weight percent; F₂ 0.72 ± 0.15 weightpercent; TiO₂ 0.10 ± 0.01 weight percent; Li₂O 0.81 ± 0.05; and SO₃ 0.02weight percent.

TABLE 1 Comparison of properties of a glass composition suitable for usein some embodiments of the present invention with properties of otherglass compositions. Glasses: Sample 1 E-Glass NE-Glass Sample 1 Relativeto E-Glass Fiber Density 2.41 2.59 2.30  7% lighter (g/cm³) FilamentTensile 3660 3010 2800 22% stronger Strength (MPa) Young's 72 73 57 sameModulus (GPa) Failure Strain 5.08 — 4.90 — (%) Linear 4.19 6.06 3.40 30%lower Coefficient of Thermal Expansion (LCTE) from 25-300° C. (10⁻⁶/ °C.) Softening Point 944 865 —  9% higher (° C.) Acid Resistance pH = 0:0.79 1.02 — 23% better at 100° C. for 1 hr 1N (% wt loss) H₂SO₄ pH = 2:<0.01 0.19 — 90% better 0.1N H₂SO₄ Refractive Index 1.518/ 1.563/ —  3%lower (bulk/fiber) 1.510 1.554 Dielectric 5.27 — 4.70 — Constant at 10GHz (D_(k)) Dissipation 0.006 — 0.004 — Factor at 10 GHz (D_(f))Dielectric >50 (0.5 mm) — >50 — Breakdown (kV) (unknown)Electrical >2450 — 1000 — Strength (V/mil) Volume 1.0 × 10¹³ — 1.0 ×10¹⁵ — Resistivity (ohm-cm)

Example 2

In this Example, the yarn break load of a yarn formed from a fiber glassstrand of the present invention (“the Sample Yarn”) was compared to ayarn made from a fiber glass strand formed from a conventional 621 glasscomposition (“the 621 Yarn”). Each of the Yarns was formed from a singlefiber glass strand having approximately 200 filaments with a nominaldiameter of 7 microns. After forming, the glass fibers were coated witha conventional starch-oil sizing compositions. The fiber glass strandswere dried and then twisted 1 turns per inch in the z direction to formthe Yarns which were then woven into a plain weave style fabric with 60picks per inch in the warp direction and 58 picks per inch in the weftdirection.

The break loads of the fabrics were then measured using ASTM 5053. A oneinch wide, 6 inch long strip of fabric was fitted with paper tabs andloaded at a speed of 12 inches per minute on a universal test frameuntil failure. A total of 12 break load measurements were taken perfabric. The average break load for the fabric strips made from theSample Yarns was 197.5 lb_(f), and the average break load for the fabricstrips made from the 621 Yarns was 181.7 lb_(f). The fabrics were thenheat cleaned and finished using the same conventional technique.Following heat cleaning and finishing the break loads of the fabricstrips were again measured using ASTM 5035. A total of 12 break loadmeasurements were taken. The average break load for the Sample fabricwas 119.5 lb_(f), and the average break load for the 621 fabric was 85.1lb_(f). The break load retention (break load after heatcleaning/finishing divided by break load prior to heat cleaningfinishing X 100) for the 621 fabric was 46.8%. The break load retention(break load after heat cleaning/finishing divided by break load prior toheat cleaning finishing) for the Sample fabric was 60.5%, demonstratingan improvement in break load over the 621 fabric.

Example 3

The tensile and impact properties of laminates of the present inventionwere compared to those of laminates made from glass fibers comprisingconventional glass compositions. In this Example, a fabric was wovenusing warp and fill yarns made from fiber glass strands having glasscompositions of the present invention (“the Sample Fabric”). Thecomparative fabric was formed from standard E-glass yarns (“E-glassFabric”). Additional details about the fabrics are provided in Table 2:

TABLE 2 Sample Fabric E-Glass Fabric Fabric Style 7781 7781 Finish 1383497-A Weave Pattern 8 HS 8HS Warp Yarn Size DE79 DE75 Fill Yarn SizeDE79 DE75 Count 57 × 61 57 × 54 Basis Weight 8.68 oz/yd² 8.73 oz/yd²Thickness 0.008″ 0.009″ Roll Length 60 yds 100 yds

The pre-impregnated fabrics were then incorporated into laminates usingvacuum assisted compression molding. The polymeric resin used was EP255modified epoxy resin from Barrday Composite Solutions, Millbury, Mass.Ten fabric layers were incorporated into each of the laminates. Theprocess conditions in Table 3 were used for the vacuum assistedcompression molding setup:

TABLE 3 Mold Temperature 255° F. Mold Time  90 minutes Mold Pressure  70psiAdequate cure of the resin was verified through determination of theglass transition temperature (T_(g)) for the composites (115.03° C. forthe Sample Laminate and 116.57° C. for the E-glass Laminate). The fiberweight fraction of the Sample Laminate was 65.72% glass, and the fiberweight fraction for the E-glass Laminate was 67.39% glass.

Tensile properties of the laminates were measured according to ISO527-4. Five Sample Laminates and five E-glass laminates were analyzed.Initial evaluation of the data suggested a slight increase in averagetensile strain to failure for the Sample Laminates with respect to theE-glass Laminates (2.15% vs. 1.95%). There were also indications ofslightly higher tensile strength and lower tensile modulus for SampleLaminates. However, these trends could not be deemed statisticallysignificant after analysis of variance (ANOVA) was performed.

The impact properties of the laminates were also measured according toASTM 3763 on specimens of equivalent thickness using a 3/8″hemispherical impactor and an instrumented impact testing machine. Theimpact properties of the Sample Laminate and the E-glass laminate wereobserved to be significantly different. In all cases, the SampleLaminates resulted in significantly increased impact performanceevidenced by high energy at maximum load, and total energy absorbed bythe samples. The average energy to maximum load was 30.984 Joules forthe Sample Laminates and 14.204 Joules for the E-glass Laminates. Theaverage total energy absorbed was 35.34 Joules for the Sample Laminatesand 26.76 Joules for the E-glass Laminates. Thus, the Sample Laminatesabsorbed on average 32% more energy than the E-glass Laminates whensubjected to the same impact velocity. Furthermore, the Sample Laminatesexhibited far less damage than the E-glass Laminates and did not reachpenetration.

Example 4

The glasses in this Example were made by melting mixtures of reagentgrade chemicals in powder form in 10% Rh/Pt crucibles at thetemperatures between 1500° C. and 1550° C. (2732° F.-2822° F.) for fourhours. Each batch was about 1200 grams. After the 4-hour melting period,the molten glass was poured onto a steel plate for quenching. Tocompensate volatility loss of B₂O₃ (typically about 5% of the totaltarget B₂O₃ concentration in laboratory batch melting condition for the1200 gram batch size), the boron retention factor in the batchcalculation was set at 95%. Other volatile species, such as fluoride andalkali oxides, were not adjusted in the batches for their emission lossbecause of their low concentrations in the glasses. The compositions inthe examples represent as-batched compositions. Since reagent chemicalswere used in preparing the glasses with an adequate adjustment of B₂O₃,the as-batched compositions illustrated are considered to be close tothe measured compositions.

Melt viscosity as a function of temperature and liquidus temperaturewere determined by using ASTM Test Method C965 “Standard Practice forMeasuring Viscosity of Glass Above the Softening Point,” and C829“Standard Practices for Measurement of Liquidus Temperature of Glass bythe Gradient Furnace Method,” respectively.

A polished disk of each glass sample with 40 mm diameter and 1-1.5 mmthickness was used for electrical property and mechanical propertymeasurements, which were made from annealed glasses. Dielectric constant(D_(k)) and dissipation factor (D_(f)) of each glass were determinedfrom 1 MHz to 1 GHz by ASTM Test Method D150 “Standard Test Methods forA-C Loss Characteristics and Permittivity (Dielectric Constant) of SolidElectrical Insulating Materials.” According to the procedure, allsamples were preconditioned at 25° C. under 50% humidity for 40 hours.Selective tests were performed for glass density using ASTM Test MethodC729 “Standard Test Method for Density of Glass by the Sink-FloatComparator,” for which all samples were annealed.

For selected compositions, a microindentation method was used todetermine Young's modulus (from the initial slope of the curve ofindentation loading—indentation depth, in the indenter unloading cycle),and microhardness (from the maximum indentation load and the maximumindentation depth). For the tests, the same disk samples, which had beentested for D_(k) and D_(f), were used. Five indentation measurementswere made to obtain average Young's modulus and microhardness data. Themicroindentation apparatus was calibrated using a commercial standardreference glass block with a product name BK7. The reference glass hasYoung's modulus 90.1 GPa with one standard deviation of 0.26 GPa andmicrohardness 4.1 GPa with one standard deviation of 0.02 GPa, all ofwhich were based on five measurements.

All compositional values in the examples are expressed in weightpercent. In the Tables below, “E” refers to Young's modulus; “H” refersto microhardness; σ_(f) refers to filament strength; and “Std” refers tostandard deviation.

Table 4 Compositions

Samples 1-8 provide glass compositions (Table 4) by weight percentage:SiO₂ 62.5-67.5%, B₂O₃ 8.4-9.4%, Al₂O₃ 10.3-16.0%, MgO 6.5-11.1%, CaO1.5-5.2%, Li₂O 1.0%, Na₂O 0.0%, K₂O 0.8%, Fe₂O₃ 0.2-0.8%, F₂ 0.0%, TiO₂0.0%, and sulfate (expressed as SO₃) 0.0%.

The glasses were found to have D_(k) of 5.44-5.67 and Df of0.0006-0.0031 at 1 MHz, and D_(k) of 5.47-6.67 and D_(f) of0.0048-0.0077 at 1 GHz frequency. The electric properties of thecompositions in Series III illustrate significantly lower (i.e.,improved) D_(k) and D_(f) over standard E-glass with D_(k) of 7.29 andD_(f) of 0.003 at 1 MHz and D_(k) of 7.14 and D_(f) of 0.0168 at 1 GHz.

In terms of fiber forming properties, the compositions in Table 4 haveforming temperatures (T_(F)) of 1300-1372° C. and forming windows(T_(F)-T_(L)) of 89-222° C. This can be compared to a standard E-glasswhich has T_(F) typically in the range 1170-1215° C. To prevent glassdevitrification in fiber forming, a forming window (T_(F)-T_(L)) greaterthan 55° C. is desirable. All of the compositions in Table 4 exhibitsatisfactory forming windows. Although the compositions of Table 4 havehigher forming temperatures than E-glass, they have significantly lowerforming temperatures than D-glass (typically about 1410° C.).

TABLE 4 Some glass compositions useful in some embodiments of thepresent invention. SAMPLES: 1 2 3 4 5 6 7 8 Al₂O₃ 11.02 9.45 11.64 12.7115.95 10.38 10.37 11.21 B₂O₃ 8.55 8.64 8.58 8.56 8.46 8.71 9.87 9.28 CaO5.10 5.15 3.27 2.48 1.50 2.95 2.01 1.54 CoO 0.00 0.00 0.00 0.00 0.000.00 0.00 0.62 Fe₂O₃ 0.39 0.40 0.39 0.39 0.39 0.53 0.80 0.27 K₂O 0.770.78 0.77 0.77 0.76 0.79 0.79 0.78 Li₂O 0.98 0.99 0.98 0.98 0.97 1.001.00 1.00 MgO 6.70 7.44 8.04 8.69 9.24 10.39 11.05 11.04 SiO₂ 66.4867.16 66.32 65.42 62.72 65.26 64.12 64.26 Properties D_(k), 1 MHz 5.625.59 5.44 5.47 5.50 5.67 5.57 5.50 D_(k), 1 GHz 5.65 5.62 5.46 5.47 5.535.67 5.56 5.50 D_(f), 1 MHz 0.0010 0.0006 0.0016 0.0008 0.0020 0.00310.0012 0.0010 D_(f), 1 GHz 0.0048 0.0059 0.0055 0.0051 0.0077 0.00510.0053 0.0049 T_(L) (° C.) 1209 1228 1215 1180 1143 1219 1211 1213 T_(F)(° C.) 1370 1353 1360 1372 1365 1319 1300 1316 T_(F) − T_(L) (° C.) 161125 145 192 222 100 89 103

Table 5 Compositions

Samples 9-15 provide glass compositions: SiO₂ 60.8-68.0%, B₂O₃ 8.6 and11.0%, Al₂O₃ 8.7-12.2%, MgO 9.5-12.5%, CaO 1.0-3.0%, Li₂O 0.5-1.5%, Na₂O0.5%, K₂O 0.8%, Fe₂O₃ 0.4%, F₂ 0.3%, TiO₂ 0.2%, and sulfate (expressedas SO₃) 0.0%.

The glasses were found to have D_(k) of 5.55-5.95 and D_(f) of0.0002-0.0013 at 1 MHz, and D_(k) of 5.54-5.94 and D_(f) of0.0040-0.0058 at 1 GHz frequency. The electric properties of thecompositions in Table 5 illustrate significantly lower (improved) D_(k)and D_(f) over standard E-glass with D_(k) of 7.29 and D_(f) of 0.003 at1 MHz, and D_(k) of 7.14 and D_(f) of 0.0168 at 1 GHz.

In terms of mechanical properties, the compositions of Table 5 haveYoung's modulus of 86.5-91.5 GPa and microhardness of 4.0-4.2 GPa, bothof which are equal or higher than standard E glass that has Young'smodulus of 85.9 GPa and microhardness of 3.8 GPa. The Young's moduli ofthe compositions in the Table 5 are also significantly higher thanD-glass which is about 55 GPa based on literature data.

In terms of fiber forming properties, the compositions of Table 5 haveforming temperature (T_(F)) of 1224-1365° C., and forming windows(T_(F)-T_(L)) of 6-105° C. as compared to standard E-glass having T_(F)in the range 1170-1215° C. Some, but not all, of the Table 5compositions have a forming window (T_(F)-T_(L)) greater than 55° C.,which is considered preferable in some circumstances to avoid glassdevitrification in commercial fiber forming operations. The Table 5compositions have lower forming temperatures than those of D-glass(1410° C.), although higher than E-glass.

TABLE 5 Some glass compositions useful in some embodiments of thepresent invention. SAMPLES: 9 10 11 12 13 14 15 Al₂O₃ 12.02 11.88 10.4112.08 12.18 8.76 12.04 B₂O₃ 10.98 10.86 9.90 8.71 8.79 8.79 8.68 CaO1.07 2.90 2.02 2.95 1.09 1.09 2.94 F₂ 0.32 0.31 0.32 0.32 0.32 0.32 0.32Fe₂O₃ 0.40 0.39 0.40 0.40 0.40 0.40 0.40 K₂O 0.78 0.77 0.79 0.79 0.790.79 0.78 Li₂O 0.50 0.49 1.00 0.50 1.51 1.51 1.49 MgO 12.35 9.56 11.1012.41 12.51 9.81 9.69 Na₂O 0.51 0.51 0.52 0.52 0.52 0.52 0.52 SiO₂ 60.8762.13 63.35 61.14 61.68 67.80 62.95 TiO₂ 0.20 0.20 0.20 0.20 0.20 0.200.20 Properties D_(k), 1 MHz 5.69 5.55 5.74 5.84 5.95 5.60 5.88 D_(k), 1GHz 5.65 5.54 5.71 5.83 5.94 5.55 5.86 D_(f), 1 MHz 0.0007 0.0013 0.00070.0006 0.0002 0.0002 0.0011 D_(f), 1 GHz 0.0042 0.0040 0.0058 0.00430.0048 0.0045 0.0053 T_(L) (° C.) 1214 1209 1232 1246 1248 1263 1215T_(F) (° C.) 1288 1314 1287 1277 1254 1365 1285 T_(F) − T_(L) (° C.) 74105 55 31 6 102 70 E (GPa) 90.5 87.4 86.8 86.5 89.6 87.2 91.5 H (GPa)4.12 4.02 4.02 4.03 4.14 4.07 4.19

TABLE 6 Some glass compositions useful in some embodiments of thepresent invention. SAMPLES: 16 17 18 19 20 Al₂O₃ 10.37 11.58 8.41 11.5812.05 B₂O₃ 8.71 10.93 10.66 8.98 8.69 CaO 2.01 2.63 3.02 1.78 2.12 F₂0.32 0.30 0.30 0.30 0.30 Fe₂O₃ 0.40 0.27 0.27 0.27 0.27 K₂O 0.79 0.250.25 0.16 0.10 Li₂O 0.50 1.21 1.53 0.59 1.40 MgO 11.06 10.04 9.65 11.6510.57 Na₂O 0.52 0.25 0.57 0.35 0.15 SiO₂ 65.13 62.55 65.35 64.35 64.35TiO₂ 0.20 0.00 0.00 0.00 0.00 Total 100.00 100.00 100.00 100.00 100.00D_(k), 1 MHz 5.43 5.57 5.30 5.42 D_(k), 1 GHz 5.33 5.48 5.22 5.33 D_(f),1 MHz 0.0057 0.0033 0.0031 0.0051 D_(f), 1 GHz 0.0003 0.0001 0.00080.0014 T_(L) (° C.) 1231 1161 1196 1254 1193 T_(F) (° C.) 1327 1262 12541312 1299 T_(F) − T_(L) (° C.) 96 101 58 58 106 T_(M) (° C.) 1703 15921641 1634 1633 E (GPa) 85.3 86.1 85.7 91.8 89.5 Std E (GPa) 0.4 0.6 2.51.7 1.5 H (GPa) 3.99 4.00 4.03 4.22 4.13 Std H (GPa) 0.01 0.02 0.09 0.080.05 SAMPLES: 21 22 23 24 25 26 Al₂O₃ 12.04 12.04 12.04 12.04 12.0412.54 B₂O₃ 8.65 8.69 10.73 10.73 11.07 8.73 CaO 2.06 2.98 2.98 2.98 2.982.88 F₂ 0.45 0.45 0.45 0.45 0.45 2.00 Fe₂O₃ 0.35 0.35 0.35 0.35 0.350.35 K₂O 0.4 0.4 0.4 0.4 0.4 0.40 Li₂O 1.53 1.05 1.05 0.59 0.48 MgO10.47 10.62 9.97 11.26 11.26 11.26 Na₂O 0.5 0.5 0.5 0.5 0.5 0.50 SiO₂63.05 62.42 61.03 60.2 59.97 61.34 TiO₂ 0.5 0.5 0.5 0.5 0.5 Total 100.00100.00 100.00 100.00 100.00 100.00 D_(k), 1 MHz 5.75 5.73 5.61 5.64 5.635.35 D_(k), 1 GHz 5.68 5.61 5.55 5.54 5.49 5.38 D_(f), 1 MHz 0.0040.0058 0.0020 0.0046 0.0040 0.0063 D_(f), 1 GHz 0.0021 0.0024 0.00340.0019 0.0023 0.0001 T_(L) (° C.) 1185 1191 1141 1171 1149 1227 T_(F) (°C.) 1256 1258 1244 1246 1249 1301 T_(F) − T_(L) (° C.) 71 67 103 75 100T_(M) (° C.) 1587 1581 1587 1548 1553 E (GPa) Std E (GPa) H (GPa) Std H(GPa) σ_(f) (KPSI/GPa) 475.7/ 520.9/ 466.5/ 522.0 3.28 3.59 3.22 Stdσ_(f) 37.3/ 18.3/ 41.8/ 18.70 (KPSI/GPa) 0.26 0.13 0.29 Density (g/cm³)2.4209* 2.4324* 2.4348*

TABLE 7 Some glass compositions useful in some embodiments of thepresent invention. SAMPLES: 27 28 E-Glass Al₂O₃ 12.42 12.57 13.98 B₂O₃9.59 8.59 5.91 CaO 0.11 0.10 22.95 F₂ 0.35 0.26 0.71 Fe₂O₃ 0.21 0.210.36 K₂O 0.18 0.18 0.11 Li₂O 0.80 1.01 0 MgO 10.25 10.41 0.74 Na₂O 0.150.18 0.89 SiO₂ 65.47 65.96 54.15 TiO₂ 0.17 0.17 0.07 D_(k), 1 MHz 5.35.4 7.3 D_(k), 1 GHz 5.3 5.4 7.1 D_(f), 1 MHz 0.003 0.008 D_(f), 1 GHz0.011 0.012 0.0168 T_(L) (° C.) 1184 1201 1079 T_(F) (° C.) 1269 12821173 T_(F) − T_(L) (° C.) 85 81 94 E (GPa) H (GPa) 3.195 3.694

Samples 29-62 provide glass compositions (Table 8) by weight percentage:SiO₂ 53.74-76.97%, B₂O₃ 4.47-14.28%, Al₂O₃ 4.63-15.44%, MgO 4.20-12.16%,CaO 1.04-10.15%, Li₂O 0.0-3.2%, Na₂O 0.0-1.61%, K₂O 0.01-0.05%, Fe₂O₃0.06-0.35%, F₂ 0.49-1.48%, TiO₂ 0.05-0.65%, and sulfate (expressed asSO₃) 0.0-0.16%.

Samples 29-62 provide glass compositions (Table 8) by weight percentagewherein the (MgO+CaO) content is 7.81-16.00%, the ratio CaO/MgO is0.09-1.74%, the (SiO₂±B₂O₃) content is 67.68-81.44%, the ratioAl₂O₃/B₂O₃ is 0.90-1.71%, the (Li₂O+Na₂O+K₂O) content is 0.03-3.38%, andthe ratio Li₂O/(Li₂O+Na₂O+K₂O) is 0.00-0.95%.

In terms of mechanical properties, the compositions of Table 8 have afiber density of 2.331-2.416 g/cm³ and an average fiber tensile strength(or fiber strength) of 3050-3578 MPa.

To measure fiber tensile strength, fiber samples from the glasscompositions were produced from a 10Rh/90Pt single tip fiber drawingunit. Approximately, 85 grams of cullet of a given composition was fedinto the bushing melting unit and conditioned at a temperature close orequal to the 100 Poise melt viscosity for two hours. The melt wassubsequently lowered to a temperature close or equal to the 1000 Poisemelt viscosity and stabilized for one hour prior to fiber drawing. Fiberdiameter was controlled to produce an approximately 10 μm diameter fiberby controlling the speed of the fiber drawing winder. All fiber sampleswere captured in air without any contact with foreign objects. The fiberdrawing was completed in a room with a controlled humidity of between 40and 45% RH.

Fiber tensile strength was measured using a Kawabata KES-G1 (Kato TechCo. Ltd., Japan) tensile strength analyzer equipped with a Kawabata typeC load cell. Fiber samples were mounted on paper framing strips using aresin adhesive. A tensile force was applied to the fiber until failure,from which the fiber strength was determined based on the fiber diameterand breaking stress. The test was done at room temperature under thecontrolled humidity between 40-45% RH. The average values and standarddeviations were computed based on a sample size of 65-72 fibers for eachcomposition.

The glasses were found to have D_(k) of 4.83-5.67 and D_(f) of0.003-0.007 at 1 GHz. The electric properties of the compositions inTable 8 illustrate significantly lower (i.e., improved) D_(k) and D_(f)over standard E-glass which has a D_(k) of 7.14 and a D_(f) of 0.0168 at1 GHz.

In terms of fiber forming properties, the compositions in Table 8 haveforming temperatures (T_(F)) of 1247-1439° C. and forming windows(T_(F)-T_(L)) of 53-243° C. The compositions in Table 8 have liquidustemperature (T_(L)) of 1058-1279° C. This can be compared to a standardE-glass which has T_(F) typically in the range 1170-1215° C. To preventglass devitrification in fiber forming, a forming window (T_(F)-T_(L))greater than 55° C. is sometimes desirable. All of the compositions inTable 8 exhibit satisfactory forming windows.

TABLE 8 Some glass compositions useful in some embodiments of thepresent invention. wt % 29 30 31 32 33 SiO₂ 64.24 58.62 57.83 61.0061.56 Al₂O₃ 11.54 12.90 12.86 12.87 12.82 Fe₂O₃ 0.28 0.33 0.33 0.33 0.32CaO 1.70 1.04 2.48 2.48 1.08 MgO 11.69 11.63 12.16 9.31 10.69 Na₂O 0.010.00 0.00 0.00 0.00 K₂O 0.03 0.03 0.03 0.03 0.03 B₂O₃ 8.96 14.28 13.1512.81 12.30 F₂ 0.53 0.62 0.61 0.61 0.65 TiO₂ 0.40 0.54 0.54 0.54 0.54Li₂O 0.60 0.00 0.00 0.00 0.00 SO₃ 0.01 0.01 0.01 0.01 0.01 Total 100.00100.00 100.00 100.00 100.00 (MgO + CaO) 13.39 12.67 14.64 11.79 11.77CaO/Mg 0.15 0.09 0.20 0.27 0.10 MgO/(MgO + CaO) 0.87 0.92 0.83 0.79 0.91SiO₂ + B₂O₃ 73.20 72.90 70.98 73.81 73.86 Al₂O₃/B₂O₃ 1.29 0.90 0.98 1.001.04 (Li₂O + Na₂O + K₂O) 0.64 0.03 0.03 0.03 0.03 Li₂O/(Li₂O + Na₂O +K₂O) 0.94 0.00 0.00 0.00 0.00 T_(L) (° C.) 1196 1228 1205 1180 1249T_(F) (° C.) 1331 1300 1258 1334 1332 T_(F) − T_(L) (° C.) 135 72 53 15483 D_(k) @ 1 GHz 5.26 *** *** 5.30 *** D_(f) @ 1 GHz 0.0017 *** ***0.001 *** Fiber density (g/cm³) *** *** *** *** *** Fiber strength (MPa)*** *** *** *** *** wt % 34 35 36 37 38 SiO₂ 63.83 65.21 66.70 60.0253.74 Al₂O₃ 10.97 10.56 10.11 12.32 15.44 Fe₂O₃ 0.26 0.25 0.24 0.29 0.24CaO 2.38 2.29 2.19 4.01 3.83 MgO 10.64 10.23 9.79 9.95 10.53 Na₂O 0.290.28 0.27 0.33 0.09 K₂O 0.03 0.03 0.03 0.03 0.03 B₂O₃ 9.32 8.96 8.5710.48 13.94 F₂ 1.20 1.16 1.11 1.35 1.48 TiO₂ 0.36 0.35 0.33 0.41 0.65Li₂O 0.70 0.67 0.64 0.79 0.02 SO₃ 0.14 0.14 0.13 0.16 0.14 Total 100.13100.13 100.12 100.15 100.13 (MgO + CaO) 13.02 12.52 11.98 13.96 14.36CaO/MgO 0.22 0.22 0.22 0.40 0.36 MgO/(MgO + CaO) 0.82 0.82 0.82 0.710.73 SiO₂ + B₂O₃ 73.15 74.17 75.27 70.50 67.68 Al₂O₃/B₂O₃ 1.18 1.18 1.181.18 1.11 (Li₂O + Na₂O + K₂O) 1.02 0.98 0.94 1.15 0.14 Li₂O/(Li₂O +Na₂O + K₂O) 0.69 0.68 0.68 0.69 0.16 T_(L) (° C.) 1255 1267 1279 10581175 T_(F) (° C.) 1313 1320 1333 1266 1247 T_(F) − T_(L) (° C.) 58 53 54208 72 D_(k) @ 1 GHz *** 5.46 5.43 5.56 5.57 D_(f) @ 1 GHz *** 0.00360.0020 0.0025 0.00437 Fiber density (g/cm³) 2.402 2.408 2.352 2.416 ***Fiber strength (MPa) 3310 3354 3369 3413 *** wt % 39 40 41 42 43 SiO₂62.54 63.83 65.21 66.70 59.60 Al₂O₃ 11.36 10.97 10.56 10.11 13.52 Fe₂O₃0.27 0.26 0.25 0.24 0.33 CaO 2.47 2.38 2.29 2.19 1.80 MgO 11.02 10.6410.23 9.79 9.77 Na₂O 0.31 0.29 0.28 0.27 0.10 K₂O 0.03 0.03 0.03 0.030.03 B₂O₃ 9.65 9.32 8.96 8.57 12.70 F₂ 1.25 1.20 1.16 1.11 1.21 TiO₂0.37 0.36 0.35 0.33 0.51 Li₂O 0.73 0.70 0.67 0.64 0.41 SO₃ 0.15 0.140.14 0.13 0.15 Total 100.14 100.13 100.13 100.12 100.14 (MgO + CaO)13.49 13.02 12.52 11.98 11.57 CaO/MgO 0.22 0.22 0.22 0.22 0.18MgO/(MgO + CaO) 0.82 0.82 0.82 0.82 0.84 SiO₂ + B₂O₃ 72.19 73.15 74.1775.27 72.30 Al₂O₃/B₂O₃ 1.18 1.18 1.18 1.18 1.06 (Li₂O + Na₂O + K₂O) 1.071.02 0.98 0.94 0.54 Li₂O/(Li₂O + Na₂O + K₂O) 0.68 0.69 0.68 0.68 0.76T_(L) (° C.) 1238 1249 1266 1276 1083 T_(F) (° C.) 1293 1313 1342 13681310 T_(F) − T_(L) (° C.) 55 64 76 92 227 D_(k) @ 1 GHz 5.45 5.31 5.395.25 5.20 D_(f) @ 1 GHz 0.00531 0.00579 0.00525 0.00491 0.00302 Fiberdensity (g/cm³) 2.403 *** *** *** *** Fiber strength (MPa) 3467 *** ****** *** wt % 44 45 46 47 48 SiO₂ 59.90 60.45 62.68 65.30 65.06 Al₂O₃13.23 13.06 12.28 11.51 12.58 Fe₂O₃ 0.34 0.35 0.20 0.19 0.25 CaO 1.861.58 1.65 1.39 1.25 MgO 10.14 10.50 8.74 8.18 6.56 Na₂O 0.10 0.10 0.100.09 0.13 K₂O 0.03 0.03 0.02 0.02 0.05 B₂O₃ 12.40 12.29 12.69 11.8910.03 F₂ 1.26 1.07 1.11 0.94 0.82 TiO₂ 0.53 0.55 0.51 0.48 0.07 Li₂O0.20 0.00 0.00 0.00 3.20 SO₃ 0.15 0.16 0.15 0.14 0.11 Total 100.14100.15 100.14 100.13 100.10 RO (MgO + CaO) 12.00 12.08 10.39 9.57 7.81CaO/Mg 0.18 0.15 0.19 0.17 0.19 MgO/(MgO + CaO) 0.85 0.87 0.84 0.85 0.84SiO₂ + B₂O₃ 72.30 72.74 75.37 77.19 75.09 Al₂O₃/B₂O₃ 1.07 1.06 0.97 0.971.25 (Li₂O + Na₂O + K₂O) 0.33 0.13 0.12 0.11 3.38 Li₂O/(Li₂O + Na₂O +K₂O) 0.61 0.00 0.00 0.00 0.95 T_(L) (° C.) 1129 1211 1201 1196 *** T_(F)(° C.) 1303 1378 1378 1439 *** T_(F) − T_(L) (° C.) 174 167 177 243 ***Dk @ 1 GHz 5.24 5.05 4.94 4.83 5.67 Df @ 1 GHz 0.00473 0.00449 0.005080.00254 0.007 Fiber density (g/cm³) 2.387 2.385 2.354 2.34 2.345 Fiberstrength (MPa) 3483 3362 3166 3050 3578 wt % 49 50 51 52 53 SiO₂ 61.1460.83 62.45 61.88 66.25 Al₂O₃ 12.90 13.02 12.52 12.72 10.60 Fe₂O₃ 0.270.28 0.26 0.28 0.18 CaO 1.72 1.74 1.59 1.63 3.33 MgO 9.25 9.36 8.98 9.135.98 Na₂O 0.10 0.10 0.10 0.10 0.86 K₂O 0.03 0.03 0.03 0.03 0.02 B₂O₃12.70 12.70 12.29 12.38 11.44 F₂ 1.16 1.17 1.08 1.10 0.90 TiO₂ 0.51 0.510.50 0.50 0.44 Li₂O 0.21 0.25 0.21 0.25 0.00 SO₃ 0.15 0.15 0.14 0.140.00 Total 100.14 100.14 100.13 100.13 100.00 (MgO + CaO) 10.97 11.1010.57 10.76 9.31 CaO/Mg 0.19 0.19 0.18 0.18 0.56 MgO/(MgO + CaO) 0.840.84 0.85 0.85 0.64 SiO₂ + B₂O₃ 73.84 73.53 74.74 74.26 77.69 Al₂O₃/B₂O₃1.02 1.03 1.02 1.03 0.93 (Li₂O + Na₂O + K₂O) 0.34 0.38 0.34 0.38 0.88Li₂O/(Li₂O + Na₂O + K₂O) 0.62 0.66 0.62 0.66 0.00 T_(L) (° C.) 1179 11791186 1191 *** T_(F) (° C.) 1342 1340 1374 1366 *** T_(F) − T_(L) (° C.)163 161 188 175 *** D_(k) @ 1 GHz *** 5.24 4.96 5.06 5.03 D_(f) @ 1 GHz*** 0.0018 0.0015 0.0014 0.0027 Fiber density (g/cm³) 2.358 2.362 2.338*** 2.331 Fiber strength (MPa) 3545 3530 3234 *** 3161 wt % 54 55 56 5758 SiO₂ 66.11 69.19 70.68 69.44 69.40 Al₂O₃ 10.58 10.37 8.87 7.20 7.21Fe₂O₃ 0.18 0.18 0.16 0.13 0.14 CaO 5.31 5.20 5.50 5.57 10.15 MgO 4.207.13 7.54 10.39 5.85 Na₂O 0.86 0.55 0.59 0.59 0.59 K₂O 0.02 0.02 0.020.02 0.02 B₂O₃ 11.41 6.39 5.72 5.80 5.79 F₂ 0.90 0.53 0.55 0.55 0.55TiO₂ 0.44 0.43 0.37 0.30 0.30 Li₂O 0.00 0.00 0.00 0.00 0.00 SO₃ 0.000.00 0.00 0.00 0.00 Total 100.00 100.00 100.00 100.00 100.00 (MgO + CaO)9.51 12.33 13.04 15.96 16.00 CaO/Mg 1.26 0.73 0.73 0.54 1.74 MgO/(MgO +CaO) 0.44 0.58 0.58 0.65 0.37 SiO₂ + B₂O₃ 77.52 75.58 76.40 75.24 75.19Al₂O₃/B₂O₃ 0.93 1.62 1.55 1.24 1.25 (Li₂O + Na₂O + K₂O) 0.88 0.57 0.610.61 0.61 Li₂O/(Li₂O + Na₂O + K₂O) 0.00 0.00 0.00 0.00 0.00 T_(L) (° C.)*** *** *** *** *** T_(F) (° C.) *** *** *** *** *** T_(F) − T_(L) (°C.) *** *** *** *** *** D_(k) @ 1 GHz *** *** *** *** *** D_(f) @ 1 GHz*** *** *** *** *** Fiber density (g/cm³) 2.341 *** *** *** *** Fiberstrength (MPa) 3372 *** *** *** *** wt % 59 60 61 62 SiO₂ 69.26 71.4574.07 76.97 Al₂O₃ 8.72 5.30 7.27 4.63 Fe₂O₃ 0.13 0.06 0.09 0.10 CaO 4.895.24 4.88 5.69 MgO 9.92 10.63 4.77 5.56 Na₂O 0.53 0.58 0.73 1.61 K₂O0.03 0.02 0.03 0.01 B₂O₃ 5.09 4.96 6.39 4.47 F₂ 0.49 0.50 0.66 0.77 TiO₂0.27 0.05 0.17 0.19 Li₂O 0.69 1.20 0.95 0.00 SO₃ 0.00 0.00 0.00 0.00Total 100.00 100.00 100.00 100.00 (MgO + CaO) 14.81 15.87 9.65 11.25CaO/Mg 0.49 0.49 1.02 1.02 MgO/(MgO + CaO) 0.67 0.67 0.49 0.49 SiO₂ +B₂O₃ 74.35 76.41 80.46 81.44 Al₂O₃/B₂O₃ 1.71 1.07 1.14 1.04 (Li₂O +Na₂O + K₂O) 1.25 1.80 1.71 1.62 Li₂O/(Li₂O + Na₂O + K₂O) 0.55 0.67 0.560.00 T_(L) (° C.) *** *** *** *** T_(F) (° C.) 1358/1355 1331/13331493/1484 *** T_(F) − T_(L) (° C.) *** *** *** *** D_(k) @ 1 GHz *** ****** *** D_(f) @ 1 GHz *** *** *** *** Fiber density (g/cm³) *** *** ****** Fiber strength (MPa) *** *** *** ***

Samples 63-73 provide glass compositions (Table 9) by weight percentage:SiO₂ 62.35-68.35%, B₂O₃ 6.72-8.67%, Al₂O₃ 10.53-18.04%, MgO 8.14-11.44%,CaO 1.67-2.12%, Li₂O 1.07-1.38%, Na₂O 0.02%, K₂O 0.03-0.04%, Fe₂O₃0.23-0.33%, F₂ 0.49-0.60%, TiO₂ 0.26-0.61%, and sulfate (expressed asSO₃) 0.0%.

Samples 63-73 provide glass compositions (Table 9) by weight percentagewherein the (MgO+CaO) content is 9.81-13.34%, the ratio CaO/MgO is0.16-0.20, the (SiO₂+B₂O₃) content is 69.59-76.02%, the ratio Al₂O₃/B₂O₃is 1.37-2.69, the (Li₂O+Na₂O+K₂O) content is 1.09-1.40%, and the ratioLi₂O/(Li₂O+Na₂O+K₂O) is 0.98.

In terms of mechanical properties, the compositions of Table 9 have afiber density of 2.371-2.407 g/cm³ and an average fiber tensile strength(or fiber strength) of 3730-4076 MPa. The fiber tensile strengths forthe fibers made from the compositions of Table 9 were measured in thesame way as the fiber tensile strengths measured in connection with thecompositions of Table 8.

The fibers formed from the compositions were found to have Young'smodulus (E) values ranging from 73.84-81.80 GPa. The Young's modulus (E)values for the fibers were measured using the sonic modulus method onfibers. Elastic modulus values for the fibers drawn from glass meltshaving the recited compositions were determined using an ultrasonicacoustic pulse technique on a Panatherm 5010 instrument fromPanametrics, Inc. of Waltham, Mass. Extensional wave reflection time wasobtained using twenty micro-second duration, 200 kHz pulses. The samplelength was measured and the respective extensional wave velocity (V_(E))was calculated. Fiber density (ρ) was measured using a MicromeriticsAccuPyc 1330 pycnometer. In general, 20 measurements were made for eachcomposition and the average Young's modulus (E) was calculated accordingto the formula E=V_(E) ²*ρ. The fiber failure strain was calculatedusing Hooke's Law based on the known fiber strength and Young's modulusvalues.

The glasses were found to have D_(k) of 5.20-5.54 and Df of0.0010-0.0020 at 1 GHz. The electric properties of the compositions inTable 9 illustrate significantly lower (i.e., improved) D_(k) and D_(f)over standard E-glass with D_(k) of 7.14 and D_(f) of 0.0168 at 1 GHz.

In terms of fiber forming properties, the compositions in Table 9 haveforming temperatures (T_(F)) of 1303-1388° C. and forming windows(T_(F)-T_(L)) of 51-144° C.

TABLE 9 Some glass compositions useful in some embodiments of thepresent invention. wt % 63 64 65 66 67 SiO₂ 64.25 65.35 66.38 67.3568.35 Al₂O₃ 11.88 11.52 11.18 10.86 10.53 Fe₂O₃ 0.26 0.25 0.24 0.24 0.23CaO 2.12 2.05 1.99 1.93 1.87 MgO 10.50 10.17 9.87 9.58 9.29 Na₂O 0.020.02 0.02 0.02 0.02 K₂O 0.04 0.03 0.03 0.03 0.03 B₂O₃ 8.67 8.40 8.157.91 7.67 F₂ 0.60 0.58 0.56 0.54 0.53 TiO₂ 0.30 0.29 0.28 0.27 0.26 Li₂O1.38 1.33 1.29 1.26 1.22 SO₃ 0.00 0.00 0.00 0.00 0.00 Total 100.00100.00 100.00 100.00 100.00 (MgO + CaO) 12.61 12.22 11.86 11.51 11.16CaO/MgO 0.20 0.20 0.20 0.20 0.20 MgO/(MgO + CaO) 0.83 0.83 0.83 0.830.83 SiO₂ + B₂O₃ 72.92 73.75 74.53 75.26 76.02 Al₂O₃/B₂O₃ 1.37 1.37 1.371.37 1.37 (Li₂O + Na₂O + K₂O) 1.40 1.36 1.32 1.28 1.24 Li₂O/(Li₂O +Na₂O + K₂O) 0.98 0.98 0.98 0.98 0.98 T_(L) (° C.) 1241 1259 1266 12681287 T_(F) (° C.) 1306 1329 1349 1374 1388 T_(F) − T_(L) (° C.) 65 70 83106 101 D_(k) @ 1 GHz 5.44 5.35 5.29 5.31 5.2 D_(f) @ 1 GHz 0.00130.0016 0.001 0.002 0.0013 Fiber density (g/cm³) 2.395 2.385 2.384 2.3752.371 Fiber strength (MPa) 3730 3759 3813 3743 3738 Young's Modulus(GPa) *** *** *** 74.25 *** Fiber failure strain (%) *** *** *** 5.04*** wt % 68 69 70 71 72 73 SiO₂ 64.39 63.63 62.87 65.45 65.61 62.35Al₂O₃ 14.05 16.04 18.04 11.05 14.29 14.74 Fe₂O₃ 0.28 0.30 0.33 0.24 0.280.29 CaO 1.90 1.79 1.67 1.91 1.77 1.79 MgO 9.39 8.77 8.14 11.44 8.7211.37 Na₂O 0.02 0.02 0.02 0.02 0.02 0.02 K₂O 0.04 0.04 0.04 0.03 0.040.04 B₂O₃ 7.75 7.23 6.72 7.80 7.19 7.28 F₂ 0.54 0.51 0.49 0.54 0.51 0.51TiO₂ 0.41 0.51 0.61 0.28 0.43 0.45 Li₂O 1.23 1.15 1.07 1.24 1.14 1.16SO₃ 0.00 0.00 0.00 0.00 0.00 0.00 Total 100.00 100.00 100.00 100.00100.00 100.00 (MgO + CaO) 11.29 10.55 9.81 13.34 10.49 13.16 CaO/MgO0.20 0.20 0.20 0.17 0.20 0.16 MgO/(MgO + CaO) 0.83 0.83 0.83 0.86 0.830.86 SiO₂ + B₂O₃ 72.14 70.87 69.59 73.25 72.80 69.63 Al₂O₃/B₂O₃ 1.812.22 2.69 1.42 1.99 2.02 (Li₂O + Na₂O + K₂O) 1.25 1.17 1.09 1.26 1.161.18 Li₂O/(Li₂O + Na₂O + K₂O) 0.98 0.98 0.98 0.98 0.98 0.98 T_(L) (° C.)1231 1219 1236 1266 1235 1220 T_(F) (° C.) 1349 1362 1368 1317 1379 1303T_(F) − T_(L) (° C.) 118 143 132 51 144 83 D_(k) @ 1 GHz 5.4 5.38 5.395.54 5.52 5.58 D_(f) @ 1 GHz 0.0016 0.0013 0.002 0.0015 0.0016 0.0015Fiber density (g/cm³) 2.393 2.398 2.407 *** *** *** Fiber strength (MPa)3954 3977 4076 *** *** *** Young's Modulus (GPa) 73.84 80.34 81.57 80.6981.80 *** Fiber failure strain (%) 5.36 4.95 5.00 4.68 4.72 ***

Desirable characteristics that can be exhibited by various but notnecessarily all embodiments of the present invention can include, butare not limited to, the following: the provision of glass fibers, fiberglass strands, glass fiber fabrics, composites, and laminates having arelatively low density; the provision of glass fibers, fiber glassstrands, glass fiber fabrics, composites, and laminates having arelatively high modulus; the provision of glass fibers, fiber glassstrands, glass fiber fabrics, composites, and laminates having arelatively high strain-to-failure; the provision of glass fibers, fiberglass strands, glass fiber fabrics, composites, laminates, and prepregsuseful for reinforcement applications; and the provision of glassfibers, fiber glass strands, glass fiber fabrics, composites, laminates,and prepregs having relatively low cost compared to other glass fibers,fiber glass strands, glass fiber fabrics, composites, laminates, andprepregs for reinforcement applications.

Various embodiments of the invention have been described in fulfillmentof the various objectives of the invention. It should be recognized thatthese embodiments are merely illustrative of the principles of thepresent invention. Numerous modifications and adaptations thereof willbe readily apparent to those of skill in the art without departing fromthe spirit and scope of the invention.

That which is claimed:
 1. A fiber glass strand comprising a plurality ofglass fibers comprising a glass composition that comprises the followingcomponents: SiO₂ 60-68 weight percent; B₂O₃ 7-12 weight percent; Al₂O₃9-15 weight percent; MgO 8-15 weight percent; CaO 0-4 weight percent;Li₂O 0-2 weight percent; Na₂O 0-1 weight percent; K₂O 0-1 weightpercent; Fe₂O₃ 0-1 weight percent; F₂ 0-1 weight percent; TiO₂ 0-2weight percent; and other constituents 0-5 weight percent total;

wherein the (Li₂O+Na₂O+K₂O) content is less than 2 weight percent andwherein the MgO content is at least twice the content of CaO on a weightpercent basis.
 2. A yarn comprising at least one fiber glass strandaccording to claim
 1. 3. The yarn of claim 2, wherein the at least onefiber glass strand is at least partially coated with a sizingcomposition.
 4. The yarn of claim 2, wherein the plurality of glassfibers have a diameter between about 5 and about 13 μm.
 5. A fabricformed from at least one fiber glass strand according to claim
 1. 6. Afabric comprising at least one fill yarn comprising at least one fiberglass strand according to claim
 1. 7. A fabric comprising at least onewarp yarn comprising at least one fiber glass strand according toclaim
 1. 8. A fabric comprising: at least one fill yarn comprising atleast one fiber glass strand according to claim 1, and at least one warpyarn comprising at least one fiber glass strand according to claim
 1. 9.The fabric of claim 8, wherein the fabric comprises a plain weavefabric, a twill fabric, a crowfoot fabric, a satin weave fabric, astitch bonded fabric, or a 3D woven fabric.
 10. A composite comprising:a polymeric resin; and glass fibers from the fiber glass strandaccording to claim 1 disposed in the polymeric resin.
 11. A compositecomprising: a polymeric resin; and at least one fabric formed from atleast one fiber glass strand according to claim
 1. 12. The composite ofclaim 11, wherein the polymeric resin comprises an epoxy resin.
 13. Thecomposite of claim 11, wherein the polymeric resin comprises at leastone of polyethylene, polypropylene, polyamide, polyimide, polybutyleneterephthalate, polycarbonate, thermoplastic polyurethane, phenolic,polyester, vinyl ester, polydicyclopentadiene, polyphenylene sulfide,polyether ether ketone, cyanate esters, bis-maleimides, and thermosetpolyurethane resins.
 14. The composite of claim 11, wherein the fabriccomprises a plain weave fabric, a twill fabric, a crowfoot fabric, asatin weave fabric, a stitch bonded fabric, or a 3D woven fabric.
 15. Anaerospace composite comprising the composite according to claim
 11. 16.An aviation composite comprising the composite according to claim 11.17. A radome comprising the composite according to claim
 11. 18. Aprepreg comprising: a polymeric resin; and at least one fiber glassstrand according to claim
 1. 19. A fiber-metal laminate comprising: theprepreg according to claim 20; a first metal sheet adhesively secured toone surface of the prepreg; and a second metal sheet adhesively securedto a second surface of the prepreg, such that the prepreg is positionedbetween the two metal sheets.
 20. The fiber-metal laminate according toclaim 19, further comprising a second prepreg according to claim 20 anda third metal sheet, wherein the second prepreg is positioned betweenthe second metal sheet and the third metal sheet.
 21. The fiber-metallaminate of claim 19, wherein the metal sheets comprise aluminum. 22.The fiber-metal laminate of claim 19, wherein the polymeric resincomprises epoxy.
 23. A laminate comprising: a polymeric resin; and aplurality of fiber glass fabrics, wherein at least one fabric is formedfrom at least one fiber glass strand according to claim
 1. 24. Acomposite comprising: a polymeric resin; and a plurality of glass fibersdisposed in the polymeric resin, wherein at least one of the pluralityof glass fibers comprises a glass composition that comprises thefollowing components: SiO2 53.5-77 weight percent; B2O3 4.5-14.5 weightpercent; Al2O3 4.5-18.5 weight percent; MgO 4-12.5 weight percent; CaO0-10.5 weight percent; Li2O 0-4 weight percent; Na2O 0-2 weight percent;K2O 0-1 weight percent; Fe2O3 0-1 weight percent; F2 0-2 weight percent;TiO2 0-2 weight percent; and other constituents 0-5 weight percenttotal.


25. The composite of claim 24, wherein the plurality of glass fibers arearranged to form a fabric.
 26. The composite of claim 24, wherein thefabric comprises a plain weave fabric, a twill fabric, a crowfootfabric, a satin weave fabric, a stitch bonded fabric, or a 3D wovenfabric.
 27. The composite of claim 24, wherein the polymeric resincomprises an epoxy resin.
 28. The composite of claim 24, wherein thepolymeric resin comprises at least one of polyethylene, polypropylene,polyamide, polyimide, polybutylene terephthalate, polycarbonate,thermoplastic polyurethane, phenolic, polyester, vinyl ester,polydicyclopentadiene, polyphenylene sulfide, polyether ether ketone,cyanate esters, bis-maleimides, and thermoset polyurethane resins. 29.An aerospace composite comprising the composite according to claim 24.30. An aviation composite comprising the composite according to claim24.
 31. A radome comprising the composite according to claim
 24. 32. Aprepreg comprising the composite according to claim
 24. 33. Afiber-metal laminate comprising: the prepreg according to claim 32; afirst metal sheet adhesively secured to one surface of the prepreg; anda second metal sheet adhesively secured to a second surface of theprepreg, such that the prepreg is positioned between the two metalsheets.
 34. The fiber-metal laminate according to claim 33, furthercomprising a second prepreg according to claim 32 and a third metalsheet, wherein the second prepreg is positioned between the second metalsheet and the third metal sheet.
 35. The fiber-metal laminate of claim33, wherein the metal sheets comprise aluminum.
 36. The fiber-metallaminate of claim 33, wherein the polymeric resin comprises epoxy.
 37. Alaminate comprising the prepreg of claim 32.